ASP.NET Core IdentityServer4 ResourceOwnerPassword with custom UserRepository - by Damain Bod:
This article shows how a custom user store or repository can be used in IdentityServer4. This can be used for an existing user management system which doesn’t use Identity or request user data from a custom source. The Resource Owner Flow using refresh tokens is used to access the protected data on the resource server. The client is implemented using IdentityModel.