IdentityServer4 as for the cross service user management

IdentityServer4 is an OpenID Connect and OAuth 2.0 framework for ASP.NET Core 2.

It enables the following features in your applications:

• Authentication as a Service: Centralized login logic and workflow for all of your applications (web, native, mobile, services). IdentityServer is an officially certified implementation of OpenID Connect.
• Single Sign-on / Sign-out: Single sign-on (and out) over multiple application types.
• Access Control for APIs: Issue access tokens for APIs for various types of clients, e.g. server to server, web applications, SPAs and native/mobile apps.
• Federation Gateway: Support for external identity providers like Azure Active Directory, Google, Facebook etc. This shields your applications from the details of how to connect to these external providers.
• Focus on Customization: The most important part - many aspects of IdentityServer can be customized to fit your needs. Since IdentityServer is a framework and not a boxed product or a SaaS, you can write code to adapt the system the way it makes sense for your scenarios.
• Mature Open Source: IdentityServer uses the permissive Apache 2 license that allows building commercial products on top of it. It is also part of the .NET Foundation which provides governance and legal backing .
• Free and Commercial Support: If you need help building or running your identity platform, let us know. There are several ways we can help you out.
  
  Reference: https://docs.identityserver. io

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