- Restore invitation code logic. Please test and add comment   to those invitation code issues that this fixes.
- Restore invitation code logic. Please test and add comment
  to those invitation code issues that this fixes.

Thanks to TNick !

wekan/wekan,GhassenRjab/wekan,wekan/wekan,wekan/wekan,libreboard/libreboard,GhassenRjab/wekan,wekan/wekan,libreboard/libreboard,wekan/wekan,GhassenRjab/wekan