fix(headless-login): simplify jwks policy checks

backend/internal/domain/hydra_models.go

@@ -10,6 +10,7 @@ const (
 	MetadataHeadlessTokenEndpointAuthMethod = "headless_token_endpoint_auth_method"
 	MetadataHeadlessJWKSURI                 = "headless_jwks_uri"
 	MetadataHeadlessJWKS                    = "headless_jwks"
+	MetadataRequestObjectSigningAlg         = "request_object_signing_alg"
 )
 
 type HydraClient struct {