Refactor URL hardcoding

[danmash]

What to refactor?

There are cases in the codebase when we are using hardcoding URLs to the project web app:

• app.models.PasswordResetLink.reset_url
• app/sendgrid/templates/reset_password.py template and usage
• app/sendgrid/templates/user_b_shared_email.py template and usage
• app/sendgrid/templates/welcome_email.py template and usage

Refactor reason

The refactoring is needed because we need the ability to use different URLs per environment:

• production with analytics https://app.climatemind.org/
• TBD production without analytics https://app-frontend-prod-001.azurewebsites.net/ (could be omitted)
• staging https://app-frontend-test-001.azurewebsites.net/
• local docker
• pytest

Suggested solution

• Update all configs from config.py to use the env variable with URL (this solution doesn't suitable for many production envs I suppose, but it's ok for now)

Acceptance criteria

• missing ENV variable shouldn't lead to an error, default config value should be prod

Tests

• manual tests
• unit tests with mocking for the class method
• integration tests with mocking for emails

[brianpeiris]

I can look into this

[danmash]

I've added env variable to staging and it works fine