Unable to detect the right GCE Service Account

[daquinoaldo]

Bug Report

The datasource is not able to detect a service account different from the project default one.

Actual Behavior and Steps to Reproduce the Problem

I'm using a dedicated service account for the Grafana instance, which is grafana@project-id.iam.gserviceaccount.com.
This service account has the bigquery.jobUser role.

Using the GCE Default Service Account Authentication Type, I get the following error.

BigQuery: Invalid project ID ''. 
Project IDs must contain 6-63 lowercase letters, digits, or dashes.
Some project IDs also include domain name separated by a colon.
IDs must start with a letter and may not end with a dash.

Using a JSON key of the same service account, it connects correctly. Moreover, if I switch back to the GCE Default Service Account Authentication Type when the key is set, it connects correctly. It connects even if I delete the key on GCP, which means it is not using the key to connect.

This means, in my opinion, that the data source is not able to detect either the Project or Client Email when the service account is not the default one.

Expected Behavior

Being able to use the instance service account even if it isn't the project one.
Reason: having multiple service accounts enables a more granularity of permissions.
Possible solution: explicitly asking for the project id and the service account email.

Specifications

• Version: latest (2.0.1, I suppose), but also 2.0.0 is affected.
• Platform: Google COS inside GCE on GCP
• Grafana Version: 7.5.4 (latest)

Related to #198. Tagging @avivl which managed the previous issue.