fix(database): cascade delete events when deleting session

[iuga]

Previously, attempting to delete a session with related events failed on Postgres due to a foreign key constraint violation. This commit adds OnDelete:CASCADE to the GORM relationship between sessions and events, ensuring that deleting a session will also remove its associated events. This resolves errors encountered during session deletion and allows safe cleanup of sessions with related events. Related to ~> #482

database error during session deletion: 
ERROR: update or delete on table "sessions" violates foreign key constraint "fk_sessions_events" on table "events" (SQLSTATE 23503)

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[gemini-code-assist]

Summary of Changes

Hello @iuga, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical database issue where deleting a session would fail if it had associated events, leading to foreign key constraint violations. By introducing a cascading delete mechanism on the session-event relationship, the system now automatically removes all related events when a session is deleted, ensuring data consistency and preventing errors during session cleanup operations.

Highlights

• Database Integrity: Implemented OnDelete:CASCADE for the Events relationship in storageSession to automatically delete associated events when a session is removed.
• Error Resolution: Fixed a foreign key constraint violation error that occurred when attempting to delete sessions with related events in Postgres.
• Data Cleanup: Ensures proper and safe cleanup of session data by automatically removing dependent event records.

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[gemini-code-assist]

Code Review

This pull request correctly resolves a foreign key constraint violation that occurred when deleting a session with associated events. By adding the constraint:OnDelete:CASCADE to the GORM struct tag, the database will now automatically delete related events when a session is deleted. The change is correct and follows best practices for handling such relationships in GORM. To improve test coverage and prevent future regressions, I recommend adding a new test case to session/database/service_test.go that specifically verifies this cascade deletion behavior. The test should create a session with events, delete the session, and then assert that the events have also been removed.