bug: GCP default Compute Engine Service Account used for Cloud Scheduler Job invocations

[jacks-reid]

Describe the bug
The Cloud Scheduler job for periodically triggering the Cloud Run service runs uses default Compute Engine Service Account credentials, which will not have permissions to invoke the Cloud Run service if the organization has removed the default IAM binding from the default Compute Engine Service Account.

It is best practice to enforce an Organization Policy to remove the default IAM bindings from default Service Accounts.

Expected behavior
The module should not rely on the existence of default IAM bindings for default Service Accounts.

Please complete the following information:

• Terraform Version: v1.4.6
• Module Version: v0.2.2