Support for the Enterprise Users API calls

[dkowis]

https://docs.gitlab.com/api/group_enterprise_users/

I discovered I actually need this, to be able to find out Enterprise User details on our usage of gitlab.com and it's not there :(

I'm hoping that this works better with enterprise Email addresses, when there isn't a proper public email address.

[dkowis]

A curl call verifies that it does give me the email, which is part of what I need to use :D

[jmini]

Can you please share the java method you are using and the curl command that you have used to compare to.

Sometimes the java models are not aligned with the actual JSON being returned by GitLab