fix: mysql referential integrity error in update_user during retire_forum

[Alam-2U]

Description

After migrating the forum backend from MongoDB to MySQL, user retirement via the retire_forum API was failing due to MySQL-specific constraints that were not handled correctly in the existing implementation.

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Issues Identified

1. Foreign Key Constraint Violation

   • The update_user logic attempted to delete ReadState (parent) records before deleting associated LastReadTime (child) records.
   • MySQL enforces referential integrity, preventing deletion of parent records while dependent child records exist.
   • This resulted in IntegrityError during user retirement.

2. Duplicate Email Constraint Violation

   • Legacy logic (inherited from MongoDB flow) sets auth_user.email = "" during user retirement.
   • In MySQL, the email field has a UNIQUE constraint, and multiple empty strings violate this constraint.
   • This caused duplicate key errors when retiring multiple users.

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Changes Made

• Fixed deletion order to maintain referential integrity

  • Explicitly delete LastReadTime (child records) before deleting ReadState (parent records).

• Removed email update from MySQL backend

  • Stopped setting auth_user.email = "" during user retirement.
  • Email handling is already managed by LMS, making this update redundant and unsafe for MySQL.

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Ticket

COSMO2-917

[Copilot]

Pull request overview

Fixes MySQL-specific failures in the retire_forum user retirement flow after the forum backend migration from MongoDB to MySQL, addressing referential integrity and uniqueness constraints.

Changes:

• Adjusts deletion order for ReadState/LastReadTime cleanup to avoid MySQL FK constraint violations.
• Stops updating auth_user.email in the MySQL backend during update_user (to avoid MySQL UNIQUE constraint collisions).
• Bumps package version to 0.5.1.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
forum/backends/mysql/api.py	Alters update_user behavior for retirement (read-state cleanup ordering and email handling).
forum/__init__.py	Version bump reflecting the fix release.

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[Akanshu-2u]

lgtm!