AuthN: Add auth proxy client (#61555)

* AuthN: set up boilerplate for proxy client

* AuthN: Implement Test for proxy client

* AuthN: parse accept list in constructor

* AuthN: add proxy client interface

* AuthN: handle error

* AuthN: Implement the proxy client interface for ldap

* AuthN: change reciever name

* AuthN: add grafana as a proxy client

* AuthN: for error returned

* AuthN: add tests for grafana proxy auth

* AuthN: swap order of grafan and ldap auth

* AuthN: Parse additional proxy headers in proxy client and pass down

pkg/services/authn/authnimpl/service.go

@@ -64,12 +64,18 @@ func ProvideService(
 		s.clients[authn.ClientAnonymous] = clients.ProvideAnonymous(cfg, orgService)
 	}
 
+	var proxyClients []authn.ProxyClient
 	var passwordClients []authn.PasswordClient
-	if !s.cfg.DisableLogin {
-		passwordClients = append(passwordClients, clients.ProvideGrafana(userService))
-	}
 	if s.cfg.LDAPEnabled {
-		passwordClients = append(passwordClients, clients.ProvideLDAP(cfg))
+		ldap := clients.ProvideLDAP(cfg)
+		proxyClients = append(proxyClients, ldap)
+		passwordClients = append(passwordClients, ldap)
+	}
+
+	if !s.cfg.DisableLogin {
+		grafana := clients.ProvideGrafana(cfg, userService)
+		proxyClients = append(proxyClients, grafana)
+		passwordClients = append(passwordClients, grafana)
 	}
 
 	// if we have password clients configure check if basic auth or form auth is enabled
@@ -84,6 +90,15 @@ func ProvideService(
 		}
 	}
 
+	if s.cfg.AuthProxyEnabled && len(proxyClients) > 0 {
+		proxy, err := clients.ProvideProxy(cfg, proxyClients...)
+		if err != nil {
+			s.log.Error("failed to configure auth proxy", "err", err)
+		} else {
+			s.clients[authn.ClientProxy] = proxy
+		}
+	}
+
 	if s.cfg.JWTAuthEnabled {
 		s.clients[authn.ClientJWT] = clients.ProvideJWT(jwtService, cfg)
 	}