Allow overriding protocol redirect_uri in OpenIdIdentityProvider from external providers

[sergiomcalzada]

When generating redirect url in the AuthenticationHandler the uri is composed from the current request protocol. When you are behind a proxy (like in a lot of Kubernetes deployments) protocol is incorrect.

You could override it in OnRedirectToIdentityProvider now, but it should be more easy to do it when configuring the options.

[Tratcher]

Duplicate of #1702