Guarded account sent in a loop when its account mail does not match $settings['guardian_mail']

Problem/Motivation

When Guardian is enabled through Configuration Management, the guardian_requirements is bypassed. This means guardian_install() function may not have updated the guarded account with the $settings['guardian_mail'], for example if this value was not available during install.

As a result, the guarded account does not have valid account data and is directly logged out again after resetting the account password or using drush uli.

Now that #2929217: guardian_form_user_form_alter() does not apply when editing user 1 as another user → is fixed, the workaround where you edit the account mail through the UI with another administrator account has been removed.

Proposed resolution

Either:

1. Update the guarded accounts mail on runtime to the $settings['guardian_mail'].
2. Display instructions after logging out how to fix the guarded account data, so the user can fix the data mismatch manually.

Remaining tasks

1. Decide on approach
2. Write a patch
3. Review
4. Commit

User interface changes

None.

API changes

None.

Data model changes

None.