ASP.NET Core authentication handler for OAuth 2.0 token introspection
https://tools.ietf.org/html/rfc7662
services.AddAuthentication(OAuth2IntrospectionDefaults.AuthenticationScheme)
.AddOAuth2Introspection(options =>
{
options.Authority = "https://base_address_of_token_service";
options.ClientId = "client_id_for_introspection_endpoint";
options.ClientSecret = "client_secret_for_introspection_endpoint";
});