🐛 : Define OAUTH2 Users as admins

[candidson]

Describe the bug
I have been using the gitlab provider for generic OAUTH2 authentication. In general, OAUTH2 users are able to successfully login. However, when these users are assigned the "administrator" roles, this doesn't appear in the "authority" payload and lead to the user not having access to the administrator pages.

To Reproduce
Steps to reproduce the behavior:

1. Set up "gitlab" provider for oauth2
2. Login with the oauth2 identity to have the identity imported in the user list
3. Login with the local admin user and set the oauth2 identity as admin
4. Log in again with oauth2 user, and check that the user isn't admin, since pages such as "users" are not available.

Expected behavior
The oauth2 user should also be configured as "administrator" and have access to admin pages such as "users".

Screenshots
"user" Payload

"authority" Payload

Desktop (please complete the following information):

• OS: Kubernetes, Ubuntu
• Browser Chrome
• Version 2.3.0-SNAPSHOT 528fc79

Additional context
None