When using GKE workload identity setting the defaultProject in the datasource configuration has no effect

[wilhelmi]

Bug Report

Expected Behavior

The ability to set the default project to something other than project running the GKE cluster.

Actual Behavior

The BigQuery connection is only established within the project hosting the GKE cluster

Steps to Reproduce the Problem

1. Deploy into a GKE cluster via Workload Identity in project-a
2. Configure the datasource:

apiVersion: 1

datasources:
- name: audit-logs
  type: doitintl-bigquery-datasource
  access: proxy
  isDefault: true
  jsonData:
       authenticationType: gce
       defaultProject: project-b
       processingLocation: US
  version: 2
  readOnly: false

1. When exploring the datasource the only project that can be selected in the query window is project-a

Specifications

• Version: latest
• Platform: GKE
• Grafana Version: 7.1.5

[codeblooded]

I believe this is actually the same issue as #317. I do not think it is specific to workload identity. I have witnessed the same behavior running on App Engine Flex. There appears to be a problem with persisting the default project when using the system service account.