docs(bigquery): Add alternative approach to setting credentials (#517)

* docs(bigquery): Add alternative approach to setting credentials * docs(bigquery): Add alternative approach to setting credentials Correction: json object rather than string * Remove trailing space Co-authored-by: Peter Lamut <plamut@users.noreply.github.com>

Author: alanyee

samples/snippets/authenticate_service_account.py

@@ -30,6 +30,11 @@ def main():
  key_path, scopes=["https://www.googleapis.com/auth/cloud-platform"],
  )
 
+ # Alternatively, use service_account.Credentials.from_service_account_info()
+ # to set credentials directly via a json object rather than set a filepath
+ # TODO(developer): Set key_json to the content of the service account key file.
+ # credentials = service_account.Credentials.from_service_account_info(key_json)
+
  client = bigquery.Client(credentials=credentials, project=credentials.project_id,)
  # [END bigquery_client_json_credentials]
  return client