Add header to http/2 calls

Author: lahirumaramba

src/app/credential-internal.ts

@@ -72,7 +72,7 @@ export class ApplicationDefaultCredential implements Credential {
 
   public getQuotaProjectId(): string | undefined {
     if (!this.quotaProjectId) {
-      this.quotaProjectId = this.authClient.quotaProjectId;
+      this.quotaProjectId = this.authClient?.quotaProjectId;
     }
     return this.quotaProjectId;
   }

src/utils/api-request.ts

@@ -1079,10 +1079,13 @@ export class AuthorizedHttpClient extends HttpClient {
       requestCopy.headers[authHeader] = `Bearer ${token}`;
 
       let quotaProjectId: string | undefined;
-      if (this.app.options.credential instanceof ApplicationDefaultCredential){
+      if (process.env.GOOGLE_CLOUD_QUOTA_PROJECT) {
+        quotaProjectId = process.env.GOOGLE_CLOUD_QUOTA_PROJECT;
+      }
+      else if (this.app.options.credential instanceof ApplicationDefaultCredential){
         quotaProjectId = this.app.options.credential.getQuotaProjectId();
       }
-      quotaProjectId = process.env.GOOGLE_CLOUD_QUOTA_PROJECT || undefined;
+
       if (!requestCopy.headers['x-goog-user-project'] && validator.isNonEmptyString(quotaProjectId)) {
         requestCopy.headers['x-goog-user-project'] = quotaProjectId;
       }

test/unit/utils/api-request.spec.ts

@@ -2569,6 +2569,9 @@ describe('AuthorizedHttpClient', () => {
     afterEach(() => {
       transportSpy!.restore();
       transportSpy = null;
+      if (process.env.GOOGLE_CLOUD_QUOTA_PROJECT) {
+        delete process.env.GOOGLE_CLOUD_QUOTA_PROJECT;
+      }
       return mockAppWithAgent.delete();
     });