Doc shepherd email does not respect deactivating an address

[jennifer-richards]

Describe the issue

A Document is linked to its shepherd via a foreign key to the Email model. If a shepherd deactivates the address used in that link, this is not automatically updated. The shepherd does have access to change that email, but they have to know about it and think to do it.

A couple fairly straightforward methods to solve this come to mind:

1. disallow deactivating the address and require the shepherd to change the emails on their documents first
2. replace the deactivated address with their primary address for them

Related to #7637

Code of Conduct

• [X] I agree to follow the IETF's Code of Conduct