docs (Consul Enterprise): Google Cloud Storage snapshot documentation (#6480)

website/source/docs/commands/snapshot/agent.html.markdown.erb

@@ -122,6 +122,9 @@ Usage: `consul snapshot agent [options]`
         "account_name": "",
         "account_key": "",
         "container_name": ""
+      },
+      "google_storage": {
+        "bucket": ""
       }
     }
   }
@@ -277,6 +280,20 @@ From Consul Enterprise version `1.5.0` onwards, you can store snapshots in Azure
 * `-azure-blob-container-name` - Container to use. Required for Azure blob storage, and setting this
   disables local storage.
 
+#### Google Cloud Storage options
+
+From Consul Enterprise version `1.6.1` onwards, you can store snapshots in Google Cloud Storage. Authentication relies on automatic discovery through the sdk as described [here](https://cloud.google.com/docs/authentication/production):
+
+* First, ADC checks to see if the environment variable GOOGLE_APPLICATION_CREDENTIALS is set. If the variable is set, ADC uses the service account file that the variable points to. The next section describes how to set the environment variable.
+
+* If the environment variable isn't set, ADC uses the default service account that Compute Engine, Kubernetes Engine, App Engine, and Cloud Functions provide, for applications that run on those services.
+
+* If ADC can't use either of the above credentials, an error occurs.
+
+This integration needs the following information:
+
+* `-gcs-bucket` supplies the bucket to use.
+
 ## Examples
 
 Running the agent with no arguments will run a long-running daemon process that will