chore: Handle conversation participation creation race condition error (#9449)

We observed some race condition errors in the conversation participation listener while trying to create a conversation participation assignment. This PR handles this error and also adds additional debug information for future.

fixes: https://linear.app/chatwoot/issue/CW-3296/activerecordrecordnotunique-pguniqueviolation-error-duplicate-key

## Changelog

- handles `ActiveRecord::RecordNotUnique, ActiveRecord::RecordInvald` errors so that they won't pollute sentry
- Adds a debug statement to log the cases
- Add previous_changes into the dispatcher so that we know the exact attribute changes which trigger `assignee_changed, team_changed` events ( would be handy in future )

app/models/concerns/assignment_handler.rb

@@ -32,7 +32,7 @@ module AssignmentHandler
       ASSIGNEE_CHANGED => -> { saved_change_to_assignee_id? },
       TEAM_CHANGED => -> { saved_change_to_team_id? }
     }.each do |event, condition|
-      condition.call && dispatcher_dispatch(event)
+      condition.call && dispatcher_dispatch(event, previous_changes)
     end
   end