feat(rq): add section on task queues

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/README.md

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+# How to send emails with Python and Mailgun
+
+To send e-mails using Python, we are going to use Mailgun, a third party service which actually delivers the messages.
+
+You could use [your own personal account and the built-in `email` and `smtp` libraries](https://blog.teclado.com/learn-python-send-emails/), but most personal e-mail providers will limit how many e-mails you can send per day. Plus, you won't get analytics and a host of other features that you can get with an email service like Mailgun.
+
+There are two ways to use the Mailgun service: [via SMTP or via their API](https://www.mailgun.com/blog/email/difference-between-smtp-and-api/). I'll show you how to use the API since it's a bit easier and has the same functionality.
+
+Sending an e-mail with Mailgun is just a matter of sending a request to their API. To do this, we'll use the `requests` library:
+
+```bash
+pip install requests
+```
+
+Remember to add it to your `requirements.txt` as well:
+
+```text title="requirements.txt"
+requests
+```
+
+## Setting up for Mailgun
+
+Before we can send any emails, we need to set up our Mailgun account. First, register over at [https://mailgun.com](https://mailgun.com).
+
+Once you have registered, select your sandbox domain. It's in [your dashboard](https://app.mailgun.com/app/dashboard), at the bottom. It looks like this: `sandbox847487f8g78.mailgun.org`. 
+
+Then at the top right, enter your personal email address under "Authorized recipients".
+
+You will get an email to confirm. Click the button that you see in that email to add your personal email to the list of authorized recipients.
+
+Next up, grab your API key. You can find it by clicking on this button (my domain and API key are blurred in this screenshot):
+
+![Click the 'Select' button to reveal your Mailgun API key](./assets/mailgun-api-key.png)
+
+## Sending emails with Mailgun
+
+To make the API request which sends an email, we'll use a function that looks very much like this one (taken from their documentation):
+
+```py
+def send_simple_message():
+    return requests.post(
+        "https://api.mailgun.net/v3/YOUR_DOMAIN_NAME/messages",
+        auth=("api", "YOUR_API_KEY"),
+        data={"from": "Excited User <mailgun@YOUR_DOMAIN_NAME>",
+            "to": ["bar@example.com", "YOU@YOUR_DOMAIN_NAME"],
+            "subject": "Hello",
+            "text": "Testing some Mailgun awesomness!"})
+```
+
+So let's go into our User resource and add a couple of imports and this function. Make sure to replace "Your Name" with your actual name or that of your application:
+
+```py title="resources/user.py"
+import os
+import requests
+
+...
+
+def send_simple_message(to, subject, body):
+    domain = os.getenv("MAILGUN_DOMAIN")
+    return requests.post(
+        f"https://api.mailgun.net/v3/{domain}/messages",
+        auth=("api", os.getenv("MAILGUN_API_KEY")),
+        data={
+            "from": f"Your Name <mailgun@{domain}>",
+            "to": [to],
+            "subject": subject,
+            "text": body,
+        },
+    )
+```
+
+Then let's go to the `.env` file and add your Mailgun API key and domain:
+
+```text title=".env"
+MAILGUN_API_KEY="1f1ahfjhf4878797887187j-5ac54n"
+MAILGUN_DOMAIN="sandbox723b05d9.mailgun.org"
+```
+
+With this, we're ready to actually send emails!

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/.env.example

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+DATABASE_URL=
+MAILGUN_API_KEY=
+MAILGUN_DOMAIN=

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/.flaskenv

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+FLASK_APP=app
+FLASK_ENV=development

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/.gitignore

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+.env
+.venv
+.vscode
+__pycache__
+data.db
+*.pyc
+.DS_Store

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/CONTRIBUTING.md

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+# CONTRIBUTING
+
+## How to run the Dockerfile locally
+
+```
+docker run -dp 5000:5000 -w /app -v "$(pwd):/app" IMAGE_NAME sh -c "flask run"
+```

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/Dockerfile

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+FROM python:3.10
+WORKDIR /app
+COPY requirements.txt .
+RUN pip install --no-cache-dir --upgrade -r requirements.txt
+COPY . .
+CMD ["/bin/bash", "docker-entrypoint.sh"]

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/README.md

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+# REST APIs Recording Project
+
+Nothing here yet!

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/app.py

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+import os
+
+from flask import Flask, jsonify
+from flask_smorest import Api
+from flask_jwt_extended import JWTManager
+from flask_migrate import Migrate
+from dotenv import load_dotenv
+
+
+from db import db
+from blocklist import BLOCKLIST
+import models
+
+from resources.item import blp as ItemBlueprint
+from resources.store import blp as StoreBlueprint
+from resources.tag import blp as TagBlueprint
+from resources.user import blp as UserBlueprint
+
+
+def create_app(db_url=None):
+    app = Flask(__name__)
+    load_dotenv()
+
+    app.config["PROPAGATE_EXCEPTIONS"] = True
+    app.config["API_TITLE"] = "Stores REST API"
+    app.config["API_VERSION"] = "v1"
+    app.config["OPENAPI_VERSION"] = "3.0.3"
+    app.config["OPENAPI_URL_PREFIX"] = "/"
+    app.config["OPENAPI_SWAGGER_UI_PATH"] = "/swagger-ui"
+    app.config["OPENAPI_SWAGGER_UI_URL"] = "https://cdn.jsdelivr.net/npm/swagger-ui-dist/"
+    app.config["SQLALCHEMY_DATABASE_URI"] = db_url or os.getenv("DATABASE_URL", "sqlite:///data.db")
+    app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False
+    db.init_app(app)
+    migrate = Migrate(app, db)
+    api = Api(app)
+
+    app.config["JWT_SECRET_KEY"] = "jose"
+    jwt = JWTManager(app)
+
+    @jwt.token_in_blocklist_loader
+    def check_if_token_in_blocklist(jwt_header, jwt_payload):
+        return jwt_payload["jti"] in BLOCKLIST
+
+    @jwt.revoked_token_loader
+    def revoked_token_callback(jwt_header, jwt_payload):
+        return (
+            jsonify(
+                {"description": "The token has been revoked.", "error": "token_revoked"}
+            ),
+            401,
+        )
+
+    @jwt.needs_fresh_token_loader
+    def token_not_fresh_callback(jwt_header, jwt_payload):
+        return (
+            jsonify(
+                {
+                    "description": "The token is not fresh.",
+                    "error": "fresh_token_required",
+                }
+            ),
+            401,
+        )
+
+    @jwt.additional_claims_loader
+    def add_claims_to_jwt(identity):
+        # Look in the database and see whether the user is an admin
+        if identity == 1:
+            return {"is_admin": True}
+        return {"is_admin": False}
+
+    @jwt.expired_token_loader
+    def expired_token_callback(jwt_header, jwt_payload):
+        return (
+            jsonify({"message": "The token has expired.", "error": "token_expired"}),
+            401,
+        )
+
+    @jwt.invalid_token_loader
+    def invalid_token_callback(error):
+        return (
+            jsonify(
+                {"message": "Signature verification failed.", "error": "invalid_token"}
+            ),
+            401,
+        )
+
+    @jwt.unauthorized_loader
+    def missing_token_callback(error):
+        return (
+            jsonify(
+                {
+                    "description": "Request does not contain an access token.",
+                    "error": "authorization_required",
+                }
+            ),
+            401,
+        )
+
+    @app.before_first_request
+    def create_tables():
+        db.create_all()
+
+    api.register_blueprint(ItemBlueprint)
+    api.register_blueprint(StoreBlueprint)
+    api.register_blueprint(TagBlueprint)
+    api.register_blueprint(UserBlueprint)
+
+    return app

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/blocklist.py

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+"""
+blocklist.py
+
+This file just contains the blocklist of the JWT tokens. It will be imported by
+app and the logout resource so that tokens can be added to the blocklist when the
+user logs out.
+"""
+
+BLOCKLIST = set()

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/db.py

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+from flask_sqlalchemy import SQLAlchemy
+
+db = SQLAlchemy()

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/docker-entrypoint.sh

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+#!/bin/sh
+
+flask db upgrade
+
+exec gunicorn --bind 0.0.0.0:80 "app:create_app()"

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/migrations/README

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+Single-database configuration for Flask.

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/migrations/alembic.ini

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+# A generic, single database configuration.
+
+[alembic]
+# template used to generate migration files
+# file_template = %%(rev)s_%%(slug)s
+
+# set to 'true' to run the environment during
+# the 'revision' command, regardless of autogenerate
+# revision_environment = false
+
+
+# Logging configuration
+[loggers]
+keys = root,sqlalchemy,alembic,flask_migrate
+
+[handlers]
+keys = console
+
+[formatters]
+keys = generic
+
+[logger_root]
+level = WARN
+handlers = console
+qualname =
+
+[logger_sqlalchemy]
+level = WARN
+handlers =
+qualname = sqlalchemy.engine
+
+[logger_alembic]
+level = INFO
+handlers =
+qualname = alembic
+
+[logger_flask_migrate]
+level = INFO
+handlers =
+qualname = flask_migrate
+
+[handler_console]
+class = StreamHandler
+args = (sys.stderr,)
+level = NOTSET
+formatter = generic
+
+[formatter_generic]
+format = %(levelname)-5.5s [%(name)s] %(message)s
+datefmt = %H:%M:%S

docs/docs/12_task_queues_emails/01_send_emails_python_mailgun/end/migrations/env.py

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+from __future__ import with_statement
+
+import logging
+from logging.config import fileConfig
+
+from flask import current_app
+
+from alembic import context
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+fileConfig(config.config_file_name)
+logger = logging.getLogger('alembic.env')
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+# from myapp import mymodel
+# target_metadata = mymodel.Base.metadata
+config.set_main_option(
+    'sqlalchemy.url',
+    str(current_app.extensions['migrate'].db.get_engine().url).replace(
+        '%', '%%'))
+target_metadata = current_app.extensions['migrate'].db.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline():
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        compare_type=True,
+        literal_binds=True
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def run_migrations_online():
+    """Run migrations in 'online' mode.
+
+    In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    # this callback is used to prevent an auto-migration from being generated
+    # when there are no changes to the schema
+    # reference: http://alembic.zzzcomputing.com/en/latest/cookbook.html
+    def process_revision_directives(context, revision, directives):
+        if getattr(config.cmd_opts, 'autogenerate', False):
+            script = directives[0]
+            if script.upgrade_ops.is_empty():
+                directives[:] = []
+                logger.info('No changes in schema detected.')
+
+    connectable = current_app.extensions['migrate'].db.get_engine()
+
+    with connectable.connect() as connection:
+        context.configure(
+            connection=connection,
+            target_metadata=target_metadata,
+            process_revision_directives=process_revision_directives,
+            compare_type=True,
+            **current_app.extensions['migrate'].configure_args
+        )
+
+        with context.begin_transaction():
+            context.run_migrations()
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()