[AIRFLOW-5513] Move example_pubsub_flow.py to GCP package

[turbaszek]

Make sure you have checked all steps below.

Jira

• My PR addresses the following Airflow Jira issues and references them in the PR title. For example, "[AIRFLOW-XXX] My Airflow PR"
  • https://issues.apache.org/jira/browse/AIRFLOW-5513

Description

• Here are some details about my PR, including screenshots of any UI changes:

Tests

• My PR adds the following unit tests OR does not need testing for this extremely good reason:

Commits

• My commits all reference Jira issues in their subject lines, and I have squashed multiple commits if they address the same issue. In addition, my commits follow the guidelines from "How to write a good git commit message":
  1. Subject is separated from body by a blank line
  2. Subject is limited to 50 characters (not including Jira issue reference)
  3. Subject does not end with a period
  4. Subject uses the imperative mood ("add", not "adding")
  5. Body wraps at 72 characters
  6. Body explains "what" and "why", not "how"

Documentation

• In case of new functionality, my PR adds documentation that describes how to use it.
  • All the public functions and the classes in the PR contain docstrings that explain what it does
  • If you implement backwards incompatible changes, please leave a note in the Updating.md so we can assign it to a appropriate release

[codecov-io]

Codecov Report

Merging #6139 into master will decrease coverage by 0.04%.
The diff coverage is 0%.

@@            Coverage Diff            @@
##           master   #6139      +/-   ##
=========================================
- Coverage   80.05%     80%   -0.05%     
=========================================
  Files         607     606       -1     
  Lines       35044   35027      -17     
=========================================
- Hits        28054   28025      -29     
- Misses       6990    7002      +12

Impacted Files	Coverage Δ
airflow/gcp/example_dags/example_pubsub.py	0% <0%> (ø)	⬆️
airflow/operators/postgres_operator.py	0% <0%> (-100%)	⬇️
airflow/hooks/postgres_hook.py	94.73% <0%> (-1.76%)	⬇️
airflow/utils/sqlalchemy.py	91.52% <0%> (-1.7%)	⬇️
airflow/hooks/dbapi_hook.py	86.44% <0%> (-1.7%)	⬇️
airflow/jobs/backfill_job.py	89.9% <0%> (-1.53%)	⬇️
airflow/jobs/scheduler_job.py	74.58% <0%> (+0.3%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7b6045a...3c3347c. Read the comment docs.

[mik-laj]

Can you explain the difference between `airflow/ contrib/example_dags/example_pubsub.py file and this file? Isn't it worth combining these two examples?

[turbaszek]

I extended the example_pubsub.py and removed the other one. Now everything is in one place.