chore: (re-)set API workers to a default of 1

[adwk67]

Description

Tests 🟢 https://testing.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/airflow-operator-it-custom/68/

Airflow code sets the default value of API_WORKERS to 4: this did not present any problems for Airflow 2.x, but was problematic in 3.x until 3.0.6, which included the version of uvicorn that honoured the timeout value that Airflow sends through.

The default of 4 is/was fine for our integration tests as the default resources have also been increased, but

• the docs were inconsistent between stating the default (4) and the recommendation (single worker)
• some users still report issues in their environments with webserver child processes being killed

This PR addresses both of the above by setting the default back to 1 and ensuring the docs are now consistent.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

Author

• Changes are OpenShift compatible
• CRD changes approved
• CRD documentation for all fields, following the style guide.
• Helm chart can be installed and deployed operator works
• Integration tests passed (for non trivial changes)
• Changes need to be "offline" compatible
• Links to generated (nightly) docs added
• Release note snippet added

Reviewer

• Code contains useful comments
• Code contains useful logging statements
• (Integration-)Test cases added
• Documentation added or updated. Follows the style guide.
• Changelog updated
• Cargo.toml only contains references to git tags (not specific commits or branches)

Acceptance

• Feature Tracker has been updated
• Proper release label has been added
• Links to generated (nightly) docs added
• Release note snippet added
• Add type/deprecation label & add to the deprecation schedule
• Add type/experimental label & add to the experimental features tracker

[sbernauer]

Many thanks for this change!

I personally would even argue this is a fix: