Recently i am working on project where i have to build simple Authentication Server. For that project i need to use Resource Owner Password (ROP) OAuth flow with persistence storage of all data. Also need to handle Social Signup/login with ROP flow. Facebook and Google as third party Identity Provider is available in this sample ( up to now)
So i am using Identity Server 4 and Entity Framework core to build this simple authentication server. This sample might be helpful if you are working on same as my requirement.
Also i am extending this sample to support other OAuth flow in future.
Here is project link in Github.