[Feature Proposal] Display name instead of / besides username for @mentions

Description

@mentions now show up as @<username> in tickets, MR's, etc. When you hover them the user's Name is displayed. We run Gitlab in an on-prem enterprise environment connected to Active Directory via LDAP, so our user accounts in Gitlab look like this:

In your typical issue or MR discussion this results in conversations like this:

Love this feature, though @u00ab12 might want to take a look at the test coverage before @u00xy89 can merge it.

This requires us to either recognize our colleagues account names or hover every @mention to display the name and get the full context of the messsage.

Proposal

To display the users name instead of / as a postfix in @mentions like this:

Love this feature, though @Stefan van Gastel might want to take a look at the test coverage before @John Doe can merge it.

or

Love this feature, though @u00ab12 (Stefan van Gastel) might want to take a look at the test coverage before @u00xy89 (John Doe) can merge it.

If the way of displaying could be configured as a personal of global Gitlab setting it would not change anything to existing behaviour, only improve it for situations where non descriptive usernames are used.

Use cases

Improves overall readability (and thus productivity) of issues, comments, merge requests, etc in cases where non descriptive usernames are used.

Feature checklist

Make sure these are completed before closing the issue, with a link to the relevant commit.