[ticket/11405] Add unit tests for post_in_queue

PHPBB3-11405
[ticket/11474] Remove invalid forum_id fallback code

The forum_id of a topic/post can not be 0 anymore

PHPBB3-11474
PHPBB3-11405
[ticket/11474] Check forum read permissions before sending notifications

PHPBB3-11474
PHPBB3-11405