If importing users from Directory, lock name changes

[Chris-Duke]

Description:

I've found that a number of users have been changing their names (in the Xmas Spirit, with Xmas Emoji's), which isn't so much a problem, but I'd prefer it if users names were kept consistent with Active Directory. I use Crowd which pulls users from Active Directory - I think it'd be useful to have an option that if you're pulling users from Active Directory either via Crowd or LDAP, that it locks Name Changes.

Server Setup Information:

• Version of Rocket.Chat Server: 0.59.4
• Operating System: Stretch
• Deployment Method(snap/docker/tar/etc): snap
• Number of Running Instances: 1
• DB Replicaset Oplog:
• Node Version: v4.8.4

[Chris-Duke]

This actually resolves the problem in this instance: #8739