Build Your Own Authentication Server for Single Sign-On (SSO) in ASP.NET Core

Discuss how to build a custom authentication server for SSO using ASP.NET Core Identity and Identity Server.

Background

On the software as a service (SaaS) market, there are quite some single sign-on providers, such as Microsoft Azure Active Directory (AD), Okta Identity Cloud. In the meantime, there are cases when off-the-shelf solutions just do NOT work or are NOT customizable enough. That is…