Update Stackdriver integration to use raw credentials

[tbroden84]

Improve use of credentials for Stackdriver, fetched from Google Service Account key when enable log and metric integrations.

New arguments

• credentials - (Optional) Google Service Account key credentials
• private_key_id - (Optional/Computed) Private key identifier from Google Service Account key

Argument updated with Computed

• project_id
• client_email
• private_key

Log & metric:
Use google_service_account_key resource from google provider to populate new argument credentials. That will base64decode the data and map it into json, to further set values for project_id, client_email, private_key, private_key_id.

resource "google_service_account_key" "service_account_key" {
  service_account_id = google_service_account.service_account.name
}

resource "cloudamqp_integration_log" "stackdriver" {
  instance_id = cloudamqp_instance.instance.id
  name = "stackdriver"
  credentials = google_service_account_key.service_account_key.private_key
}

resource "cloudamqp_integration_metric" "stackdriver" {
  instance_id = cloudamqp_instance.instance.id
  name = "stackdriver"
  credentials = google_service_account_key.service_account_key.private_key
}

Make sure to exclude argument tags if not used or set to "" in request body.

Old way to add the private_key is still supported. But clarified in documentation on what decoding is needed.

resource "cloudamqp_integration_log" "stackdriver" {
  ...
  private_key = jsondecode(base64decode(google_service_account_key.service_account_key.private_key)).private_key
}

Metrics:
Make sure to exclude arguments queue_allowlist, vhost_allowlist if not used or set to "" in request body.