[management] Skip JWT group evaluation for embedded-IdP local users (#6422)

When JWT group sync is enabled with a restrictive JWTAllowGroups list, the local owner of an embedded-IdP (Dex) deployment can get locked out. The allow-groups check runs account-wide but local password users do not receive
external IdP group claims, so they can't satisfy the allowed list.

This skips JWT group evaluation for local Dex users so the restriction and JWT group sync continue to apply to external-IdP users as intended.

idp/dex/provider.go

@@ -41,6 +41,8 @@ type Config struct {
 	GRPCAddr string
 }
 
+const localConnectorID = "local"
+
 // Provider wraps a Dex server
 type Provider struct {
 	config       *Config
@@ -544,7 +546,7 @@ func (p *Provider) CreateUser(ctx context.Context, email, username, password str
 
 	// Encode the user ID in Dex's format: base64(protobuf{user_id, connector_id})
 	// This matches the format Dex uses in JWT tokens
-	encodedID := EncodeDexUserID(userID, "local")
+	encodedID := EncodeDexUserID(userID, localConnectorID)
 	return encodedID, nil
 }
 
@@ -619,6 +621,13 @@ func DecodeDexUserID(encodedID string) (userID, connectorID string, err error) {
 	return userID, connectorID, nil
 }
 
+// IsLocalUserID reports whether encodedID is a Dex subject for the built-in
+// local password connector.
+func IsLocalUserID(encodedID string) bool {
+	_, connectorID, err := DecodeDexUserID(encodedID)
+	return err == nil && connectorID == localConnectorID
+}
+
 // GetUser returns a user by email
 func (p *Provider) GetUser(ctx context.Context, email string) (storage.Password, error) {
 	return p.storage.GetPassword(ctx, email)

idp/dex/provider_test.go

@@ -115,6 +115,26 @@ func TestDecodeDexUserID(t *testing.T) {
 	}
 }
 
+func TestIsLocalUserID(t *testing.T) {
+	tests := []struct {
+		name      string
+		encodedID string
+		want      bool
+	}{
+		{name: "local connector", encodedID: EncodeDexUserID("7aad8c05-3287-473f-b42a-365504bf25e7", "local"), want: true},
+		{name: "federated connector", encodedID: EncodeDexUserID("entra-user", "entra"), want: false},
+		{name: "non-dex external IdP id", encodedID: "google-oauth2|1234567890", want: false},
+		{name: "invalid base64", encodedID: "not-valid-base64!!!", want: false},
+		{name: "empty", encodedID: "", want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, IsLocalUserID(tt.encodedID))
+		})
+	}
+}
+
 func TestEncodeDexUserID(t *testing.T) {
 	userID := "7aad8c05-3287-473f-b42a-365504bf25e7"
 	connectorID := "local"