* EXreaction/ticket/11413: (23 commits)
[ticket/11413] Revert some cache service related changes from earlier
[ticket/11413] Use phpbb_user in test
[ticket/11413] $user should have been $this->user
[ticket/11413] Fix unit tests
[ticket/11413] Translate the error
[ticket/11413] Rename file to something more helpful
[ticket/11413] Remove remaining irrelevant code to this PR
[ticket/11413] Remove mock sql_insert_buffer.php (not relevant to PR)
[ticket/11413] Remove conversion of user_notifications
[ticket/11413] Correct copyright year
[ticket/11413] Remove changes for ticket 11420 from this branch
[ticket/11413] Include mock class
[ticket/11413] Don't use the database for the convert test
[ticket/11413] Test get_notification_type_id and _ids functions
[ticket/11413] Use sql_insert_buffer
[ticket/11413] Create test for notification conversion
[ticket/11413] Fix test fixtures and tests
[ticket/11413] Fix some more tests
[ticket/11413] Fix notification tests
[ticket/11413] Prevent recursive function calls
...