[ux] quick form to create new clients does not distinguish between ldap users and others

[pedro-nonfree]

the confusion is that the form to create new clients "enter valid ldap user email" accepts both ldap users and non ldap users, in the peer list, the two types of users are not distinguishable

I see two ways to solve it:

• one solution would be to not accept emails that are not from the ldap sync filter (or when ldap is enabled)
• another solution would be to make it easy to distinguish between users added from ldap and the others added to the database

this is important to track what users are going to be correctly disabled when are not part of the ldap sync filter (because they lost the specific membership, or they are not in the ldap database anymore - yay, this works and is amazing), from the other users added manually and that needs to be removed manually