[NEW] Added support for Dataporten's userid-feide scope

[torgeirl]

@RocketChat/core

Dataporten has two OAuth scopes for usernames. In addition to the userid scope (an unique string) currently supported by Rocket.Chat a more human-readable userid-feide scope (an unique username) is available as explained in Dataporten's documentation.

With this commit, if the Rocket.Chat administrator add the userid-feide scope to your app's configuration in the Dataporten Dashboard, the username will be set to the unique username over the unique string.

Screenshot
Dataporten login with the test user eva_student before and after the changes in the commit:

Of note, the test user's username has a slightly different form than a real user's would. Ie. the user ola at the Norwegian University of Science and Technology (NTNU) would be named feide:ola@ntnu.no.

[torgeirl]

This is sort-of related to issue #3580, fixed when @kasperrt added support for the userid scope.