title: How to setup IdentityServer4 to be an external identity provider
body: <p>There is a lot of information and documentation available regarding how to add external identity providers such as Google, Facebook, Microsoft, etc.</p>
  <p>Does IdentityServer4 support <em>being</em> the external identity provider for another for another OpenID Connect server (perhaps another IdentityServer4 instance)?</p>
  <p>If so, how do you set this up? If my IdentityServer4 instance (Instance A) is acting as the external provider for another IdentityServer4 instance (Instance B), what kind of client do I need to setup on Instance A for Instance B?</p>
  <p>Any documentation or samples on the subject would be extremely helpful.</p>