The update_player_id event handler lacks test coverage. #300
Description
The update_player_id event handler lacks test coverage. Given that this feature involves critical player identity management with potential race conditions and state consistency concerns, tests should be added to verify: 1) successful player ID updates, 2) handling of non-existent old_player_id, 3) concurrent update scenarios, and 4) proper error handling for malformed events. Test examples can be found in auth_integration_tests.rs for similar event handlers.
Originally posted by @Copilot in #299 (comment)