Improve error messages on failed onboarding (#17357)

packages/core/src/utils/errors.ts

@@ -81,6 +81,13 @@ export class ForbiddenError extends Error {}
 export class UnauthorizedError extends Error {}
 export class BadRequestError extends Error {}
 
+export class ChangeAuthRequestedError extends Error {
+  constructor() {
+    super('User requested to change authentication method');
+    this.name = 'ChangeAuthRequestedError';
+  }
+}
+
 interface ResponseData {
   error?: {
     code?: number;

packages/core/src/utils/googleQuotaErrors.ts

@@ -63,7 +63,7 @@ export class ValidationRequiredError extends Error {
 
   constructor(
     message: string,
-    override readonly cause: GoogleApiError,
+    override readonly cause?: GoogleApiError,
     validationLink?: string,
     validationDescription?: string,
     learnMoreUrl?: string,