feat(ID token support): Add ID token support for authenticating to MC… (#12031)

Co-authored-by: Adam Weidman <adamfweidman@google.com>

packages/core/src/config/config.ts

@@ -193,6 +193,8 @@ export class MCPServerConfig {
     // OAuth configuration
     readonly oauth?: MCPOAuthConfig,
     readonly authProviderType?: AuthProviderType,
+    // When true, use Google ADC to fetch ID tokens for Cloud Run
+    readonly allow_unscoped_id_tokens_cloud_run?: boolean,
     // Service Account Configuration
     /* targetAudience format: CLIENT_ID.apps.googleusercontent.com */
     readonly targetAudience?: string,