[AIRFLOW-4316] support setting kubernetes_environment_variables config section from env var

[houqp]

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-5055

Description

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When AIRFLOW_KUBERNETES_ENVIRONMENT_VARIABLES__AIRFLOW_HOME is set in
the scheduler, AIRFLOW_HOME should be set for workers, not airflow_home. This means kubernetes_environment_variables section's keys need to be parsed with case sensitivity.

Tests

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Updated test in test_env_var_config to capture the requirement.

Commits

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  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

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Code Quality

• Passes flake8

[ashb]

Please update PR title and commit message to target AIRFLOW-4316 too

[houqp]

I decided to leave kubernetes_environment_variables as a special case to avoid breaking all the existing setups. I have left a comment in the code to explain what it is needed.

@ashb please let me know you think we should go the other route instead, i.e. make all environment variable case sensitive.