[management, reverse proxy] Add reverse proxy feature (#5291)

* implement reverse proxy


---------

Co-authored-by: Alisdair MacLeod <git@alisdairmacleod.co.uk>
Co-authored-by: mlsmaycon <mlsmaycon@gmail.com>
Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: Viktor Liu <viktor@netbird.io>
Co-authored-by: Diego Noguês <diego.sure@gmail.com>
Co-authored-by: Diego Noguês <49420+diegocn@users.noreply.github.com>
Co-authored-by: Bethuel Mmbaga <bethuelmbaga12@gmail.com>
Co-authored-by: Zoltan Papp <zoltan.pmail@gmail.com>
Co-authored-by: Ashley Mensah <ashleyamo982@gmail.com>

management/server/idp/embedded.go

@@ -91,6 +91,12 @@ func (c *EmbeddedIdPConfig) ToYAMLConfig() (*dex.YAMLConfig, error) {
 	cliRedirectURIs = append(cliRedirectURIs, "/device/callback")
 	cliRedirectURIs = append(cliRedirectURIs, c.Issuer+"/device/callback")
 
+	// Build dashboard redirect URIs including the OAuth callback for proxy authentication
+	dashboardRedirectURIs := c.DashboardRedirectURIs
+	baseURL := strings.TrimSuffix(c.Issuer, "/oauth2")
+	// todo: resolve import cycle
+	dashboardRedirectURIs = append(dashboardRedirectURIs, baseURL+"/api/reverse-proxy/callback")
+
 	cfg := &dex.YAMLConfig{
 		Issuer: c.Issuer,
 		Storage: dex.Storage{
@@ -118,7 +124,7 @@ func (c *EmbeddedIdPConfig) ToYAMLConfig() (*dex.YAMLConfig, error) {
 				ID:           staticClientDashboard,
 				Name:         "NetBird Dashboard",
 				Public:       true,
-				RedirectURIs: c.DashboardRedirectURIs,
+				RedirectURIs: dashboardRedirectURIs,
 			},
 			{
 				ID:           staticClientCLI,