Add ability for IATI Admin users to block spam email addresses

[emmajclegg]

There has been an increase in spam IATI Publisher accounts being created - IATI Admins want to be able to delete and then block these users from creating an account again in future.

When we go to delete a user from IATI Publisher, can we add an optional functionality to also block the email address?

(We are blocking these spam users across other IATI tools, including the Registry and IATI Connect)

[PG-Momik]

@emmajclegg we can work on this.

We could add a simple checkbox on this modal to flag a email as spam.

The flagged emails can then be stored in separate spam_emails table. We could then prevent new registration from said emails if it exits on spam_emails table.

I'll update this issue with a breakdown of possible tasks.

[emmajclegg]

Based on the solution you've proposed for #1384 @PG-Momik , I no longer think we need the ability to block user email addresses from the User page as well. If we can block the email address associated with an organisation when we delete the organisation, that should be sufficient.