Edit user role table changes null out the user's email

[petertgiles]

🐛 Bug

The role tables on the edit user page use the same mutation from the edit user page itself. However, this mutation is set to null out empty email addresses. Since the role dialogs do not provide an email address they null out the email field for the user.

🦋 Expected Behaviour

Role edits should not affect the user's email address

🕵️ Details

It seems like this behaviour was added in #4103.

📋 Steps to Reproduce

1. Navigate to http://localhost:8000/en/admin/users/{userId}/edit
2. Ensure the user has an email address in their profile
3. Make any role change
4. Observe that the email is gone

📸 Screenshot

Add a screenshot (if possible).

🙋‍♀️ Proposed Solution

Perhaps the page should pass a separate mutation to the role tables? Or the role tables should manage their own mutations?

✅ Acceptance Criteria

• Role changes no longer affect the email address
• Whatever PR Bug - Improve unique email validation #4103 fixed is not regressed