Improved handling of inactive users

[torgeirl]

User case

Django admin UI is quite limited in its handling of user deletion; Trix 2.1 only has filters for super users and last login (today, last seven days, this month, this year, no login date, or has login date).

With the consent form introduced in 2.1.0 (#21) it would also be nice to filter whether users has signed the consent form or not.

Solutions

1. CLI commands
CLI commands that allow system administrators to delete inactive users more targeted than Django admin UI, similar to Devilry's management command:

venv/bin/python manage.py devilry_delete_inactive_users "YYYY-MM-DD HH:MM"

This could be combined with an option to keep users older than the provided date, if they have signed consent form.

2. Extend Django admin filters
Add more filters to /trix_core/user:

• Has signed concent form: All/Yes/No
• Last login: add before this semester and before last semester (could require trix_settings.py definition of semesters)