ENHANCEMENT - External Authentication for Managed Users

[zanewgray]

Is your feature request related to a problem? Please describe.
Enhancement - Add external authentication provider options (e.g. LDAP or Active Directory) to the Manage Users section.

Describe the solution you'd like
When using NGINX UI in a multi-user environment, the Manage Users section should provide other alternatives for configuring remote authentication sources and adding administrative users from those authentication sources. Such sources may include OAuth, Active Directory, LDAP, and SAML. This allows better life-cycle management of user credentials and administrative management.

Describe alternatives you've considered
Possible scripting of user credentials, but unsure where NGINX UI stores this information. Possible integration between the NGINX UI and the underlying OS' authentication settings (e.g. NGINX and NGINX UI on Ubuntu with Ubuntu registered to Active Directory for authentication and NGINX UI using Ubuntu as the authentication provider).

Additional context
Add any other context or screenshots about the feature request here.