feat: add auto assign calls when a feed is added

[davidgamez]

From our AI friend

This pull request introduces automated license assignment for feeds based on their license_url, improving data quality and reducing manual review. The core change is the new assign_license_by_url function, which resolves and assigns a license to a feed if a confident match is found, and records the assignment with a verification status. The implementation is integrated into both the database population scripts and the API feed creation endpoints. Additionally, a new verified column is added to the feed_license_change table to track whether an assignment was auto-verified or requires human review. Comprehensive unit tests are included for the new assignment logic.

Automated license assignment and verification:

• Added assign_license_by_url to license_utils.py, which resolves and assigns a license to a feed using its license_url, auto-verifies high-confidence matches, and records the assignment in feed_license_changes with a verified flag.
• Updated GTFS and GBFS database population scripts (populate_db_gtfs.py, populate_db_gbfs.py) to call assign_license_by_url when adding new feeds with a license_url. [1] [2]
• Integrated license assignment into the API endpoints for GTFS and GTFS-RT feed creation, ensuring licenses are assigned and committed after feed creation. [1] [2]

Database and model updates:

• Added a verified column to the feed_license_change table to indicate whether a license assignment was auto-verified or needs human review.
• Updated the task executor's assign_feed_license to set the verified flag using the same confidence threshold logic as assign_license_by_url. [1] [2]

Testing and reliability:

• Added comprehensive unit tests for assign_license_by_url covering all key behaviors, including no match, single/multiple matches, verification threshold, and duplicate assignment prevention.

These changes automate and standardize license assignment for feeds, improving accuracy and auditability while reducing manual intervention.

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