* Feature: Allow assign on groups
* Use type: group_list option
* Track group changes and update the setting accordingly. Restrict reminders frequency to assign allowed users instead of staff
* FEATURE: Users can override reminders frequency
* Changes:
- Avoid creating a user custom field when the used didn't override the frequency
- Sanitize frequency value using coercion
- Minor fixes
* Sanitize query and user query single
* FEATURE: Limit the amount of assigned topics an user can have.
* Do not enfore the limit when self-assigning
* Avoid computing the query when self-assigning. Do not count self-assigns when enforcing the limit
* FEATURE: Remind users of assigned tasks.
* User an user custom field instead of adding a new column
* Improve tests. fix assigns count and display oldest assigned topics correctly. Do not remind about recently assigned tasks