* FEATURE: add "assigned:<name>" filter (in the /filter page)
The "assigned:<name>" filter was already available in the advanced
search but it wasn't in the /filter page.
This commit adds that filter allowing anyone to filter topics assigned
to either a specific user (using their username) or to a specific group
(using its name).
* DEV: use argument instead of instance variable
* SPEC: add spec for when the user can't assign
After a topic is closed, the assignment is not deleted but becomes
inactive. When this happened, it was not removed from the assignments
count or list.
Change `topic_id` to polymorphic approach (In the next step we will allow assigning to individual post)
`topic_id` column is still used for efficient display of assigned users on topic list (to avoid scanning posts)
Ability to assign groups.
To assign group, user must have a right to send a message to that group.
In addition, 2 jobs were introduced, - AssignNotification and UnassignNotification to inform interested users in the background about the new assignment.
This significantly reduces the amount of logic we need to carry in the discourse-assign plugin. One side effect is that I had to rename the 'q' parameter to 'search', so that it matches core's implementation.
Régis Hanol
Natalie Tay
David Taylor
Rafael dos Santos Silva
Bianca Nenciu
Krzysztof Kotlarek
Jarek Radosz
Ahmed Gagan