feat: turns on self-signed JWT feature flag (#100)

- [ ] Regenerate this pull request now.

PiperOrigin-RevId: 392067151

Source-Link: googleapis/googleapis@06345f7

Source-Link: googleapis/googleapis-gen@95882b3

Author: gcf-owl-bot[bot]

packages/google-cloud-bigquery-reservation/src/v1/reservation_service_client.ts

@@ -145,6 +145,12 @@ export class ReservationServiceClient {
     // Save the auth object to the client, for use by other methods.
     this.auth = this._gaxGrpc.auth as gax.GoogleAuth;
 
+    // Set useJWTAccessWithScope on the auth object.
+    this.auth.useJWTAccessWithScope = true;
+
+    // Set defaultServicePath on the auth object.
+    this.auth.defaultServicePath = staticMembers.servicePath;
+
     // Set the default scopes in auth client if needed.
     if (servicePath === staticMembers.servicePath) {
       this.auth.defaultScopes = staticMembers.scopes;