[#5052] Allow users to request account closure

[chrismytton]

Relevant issue(s)

Fixes #5052

What does this do?

Adds a "Close account" link to the users profile, which when clicked takes the user to a confirmation screen explaining what happens when an account is closed. If they confirm then an account closure request is created and a confirmation email is sent to the user.

There is then a list of account closure requests in the admin which an admin can go through. That list has a link to the user's account, and a close button, which closes the account directly.

Why was this needed?

• Allow users to request to have their accounts closed.
• To reduce the administrative workload related to "right to erasure" requests.

Implementation notes

• Adds a Users::CloseAccountController with new and create actions for users to request account closure.
• Adds an AccountClosureRequest model to manage closure requests.
• Sends email notifications to users upon request of account closure.
• Updates admin interface to allow viewing and management of account closures.
• Adds links for account closure in both user profile and admin interface.

Video

Screen.Recording.2023-08-29.at.08.29.24-silent.mov

Notes to reviewer

• Should the user be logged out after they have requested account closure?
• Should the "Close account" button on the user's profile be more (or less!) prominent?
• Is it now too easy for an admin to close an account?
• Should the list of account closure requests be added to the admin homepage "todo" list?