Reactivate user button

[eatyourpeas]

see #813
Rather than delete a user, instead deletion converted to deactivation. Retains referential integrity this way for related models and good for user audit trail.
Inactive users now viewable in the UI, but need a way of reactivating by those with appropriate permissions should they need.
Suggested work flow:

• add button to user table
• new post request url for reactivate user. Could add additional feature to email user to say account now active.
• new htmx post request function in view to reactivate user - set is_active flag on user to True