fix: Deserialization issue

[Prajwal-Microsoft]

Purpose

This pull request improves the serialization of processed output in the GapExecutor to handle Python datetime objects, preventing serialization errors during workflow execution. It also adds comprehensive unit tests to ensure datetime values are correctly serialized.

Serialization improvements:

• Added a _json_default method to GapExecutor to convert datetime, date, and time objects to ISO format strings for JSON serialization, and updated the serialization logic in _serialize_processed_output to use this method. This prevents failures when serializing processed output containing these types. [1] [2] [3]

Testing enhancements:

• Introduced a new TestSerializeProcessedOutput test class to verify that GapExecutor._serialize_processed_output correctly serializes dictionaries containing nested datetime values. [1] [2]

Does this introduce a breaking change?

• Yes
• No

Golden Path Validation

• I have tested the primary workflows (the "golden path") to ensure they function correctly without errors.

Deployment Validation

• I have validated the deployment process successfully and all services are running as expected with this change.

What to Check

Verify that the following are valid

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