fix(databricks): update DatabricksJobRunLink for improved XCom handlin

[mohamedmeqlad99]

Fix Databricks Extra Link to See Job Run with Custom S3 Backend

Problem Addressed

This PR addresses the issue described in #45240, where the Databricks Extra Link for "See Job Run" does not work when using a custom XCom backend that writes to S3. Specifically:

• The link directs to the S3 path of the XCom JSON file instead of the Databricks workspace job run URL.
• This behavior makes the feature unusable in setups with custom XCom backends, such as those storing XCom values entirely in S3.

Proposed Changes

• Refactored the DatabricksJobRunLink implementation to reliably fetch the Databricks job run URL from XCom using XCom.get_value.
• Ensured compatibility with custom XCom backends, decoupling the link generation logic from specific backend implementations.
• Improved error handling to ensure the system fails gracefully if the required XCom value is missing or malformed.
• Enhanced maintainability with detailed comments and a cleaner structure.

Key Benefits

• Resolves the issue of broken links when using custom XCom backends.
• Ensures compatibility across a wide range of backend configurations, including setups where all XCom values are stored in S3.
• Improves user experience by providing accurate links to Databricks job run details.

Testing

• Validated the new implementation using a local Airflow environment with a custom XCom backend.
• Confirmed that the generated links now correctly point to Databricks job run URLs, regardless of the XCom storage location.

Issue Link

Closes #45240.

Checklist

• All unit tests pass.
• Code is formatted according to Airflow’s standards.
• Changes are backward compatible and do not break existing functionality.

Code of Conduct

I agree to follow this project's Code of Conduct.

[boring-cyborg]

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[potiuk]

You need to add unit tests exhibiting and testing the new behaviour

[mohamedmeqlad99]

@potiuk i don't understand can u explain more how can I do this and what I need to edit

[potiuk]

Add unit tests: Look at our Contributing docs - particularly testing - you can also look at other PRs for reference. We practically never accept PRs that have no accompanying unit tests and you need to learn how to write and run them if you want to contribute.

Our contribution guides have quick-starts for various IDEs and when you follow them you can have working development environment where you can run unit tests in less than 10 minutes.