Auth provider cannot be found if missing "auth.provider" prefix

[ojathelonius]

The auth provider offered by this plugin cannot be found unless the "auth.provider" prefix is used in services.xml, and yields the following stacktrace :

General Error
No suitable auth plugin found.

BACKTRACE

FILE: (not given by php)
LINE: (not given by php)
CALL: msg_handler()

FILE: [ROOT]/includes/acp/acp_board.php
LINE: 636
CALL: trigger_error()

FILE: [ROOT]/includes/functions_module.php
LINE: 676
CALL: acp_board->main()

FILE: [ROOT]/adm/index.php
LINE: 82
CALL:  #p_master->load_active()

Please see #3 to fix the issue. Purging the cache is necessary after applying the chances.