Add "response_modes_supported" to Supervisor discovery response.

Signed-off-by: Matt Moyer <moyerm@vmware.com>

internal/oidc/discovery/discovery_handler.go

@@ -25,6 +25,7 @@ type Metadata struct {
 	JWKSURI               string `json:"jwks_uri"`
 
 	ResponseTypesSupported           []string `json:"response_types_supported"`
+	ResponseModesSupported           []string `json:"response_modes_supported"`
 	SubjectTypesSupported            []string `json:"subject_types_supported"`
 	IDTokenSigningAlgValuesSupported []string `json:"id_token_signing_alg_values_supported"`
 
@@ -63,6 +64,7 @@ func NewHandler(issuerURL string) http.Handler {
 		JWKSURI:                           issuerURL + oidc.JWKSEndpointPath,
 		SupervisorDiscovery:               SupervisorDiscoveryMetadataV1Alpha1{PinnipedIDPsEndpoint: issuerURL + oidc.PinnipedIDPsPathV1Alpha1},
 		ResponseTypesSupported:            []string{"code"},
+		ResponseModesSupported:            []string{"query", "form_post"},
 		SubjectTypesSupported:             []string{"public"},
 		IDTokenSigningAlgValuesSupported:  []string{"ES256"},
 		TokenEndpointAuthMethodsSupported: []string{"client_secret_basic"},

internal/oidc/discovery/discovery_handler_test.go

@@ -43,6 +43,7 @@ func TestDiscovery(t *testing.T) {
 					PinnipedIDPsEndpoint: "https://some-issuer.com/some/path/v1alpha1/pinniped_identity_providers",
 				},
 				ResponseTypesSupported:            []string{"code"},
+				ResponseModesSupported:            []string{"query", "form_post"},
 				SubjectTypesSupported:             []string{"public"},
 				IDTokenSigningAlgValuesSupported:  []string{"ES256"},
 				TokenEndpointAuthMethodsSupported: []string{"client_secret_basic"},

test/integration/supervisor_discovery_test.go

@@ -479,6 +479,7 @@ func requireWellKnownEndpointIsWorking(t *testing.T, supervisorScheme, superviso
       "jwks_uri": "%s/jwks.json",
       "scopes_supported": ["openid", "offline"],
       "response_types_supported": ["code"],
+      "response_modes_supported": ["query", "form_post"],
       "claims_supported": ["groups"],
       "discovery.supervisor.pinniped.dev/v1alpha1": {"pinniped_identity_providers_endpoint": "%s/v1alpha1/pinniped_identity_providers"},
       "subject_types_supported": ["public"],