Add auth example to gitaly client docs

doc/administration/gitaly/configure_gitaly.md

@@ -378,13 +378,26 @@ server (with `gitaly_address`) unless you use
 1. Edit `/etc/gitlab/gitlab.rb`:
 
    ```ruby
+   # Use the same token value configured on all Gitaly servers
+   gitlab_rails['gitaly_token'] = '<AUTH_TOKEN>'
+
    git_data_dirs({
-     'default' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
+     'default'  => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
      'storage1' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
      'storage2' => { 'gitaly_address' => 'tcp://gitaly2.internal:8075' },
    })
    ```
 
+   Alternatively, if each Gitaly server is configured to use a different authentication token:
+
+   ```ruby
+   git_data_dirs({
+     'default'  => { 'gitaly_address' => 'tcp://gitaly1.internal:8075', 'gitaly_token' => '<AUTH_TOKEN_1>' },
+     'storage1' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075', 'gitaly_token' => '<AUTH_TOKEN_1>' },
+     'storage2' => { 'gitaly_address' => 'tcp://gitaly2.internal:8075', 'gitaly_token' => '<AUTH_TOKEN_2>' },
+   })
+   ```
+
 1. Save the file and [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure).
 1. Run `sudo gitlab-rake gitlab:gitaly:check` on the Gitaly client (for example, the
    Rails application) to confirm it can connect to Gitaly servers.
@@ -404,12 +417,15 @@ server (with `gitaly_address`) unless you use
        storages:
          default:
            gitaly_address: tcp://gitaly1.internal:8075
+           gitaly_token: AUTH_TOKEN_1
            path: /some/local/path
          storage1:
            gitaly_address: tcp://gitaly1.internal:8075
+           gitaly_token: AUTH_TOKEN_1
            path: /some/local/path
          storage2:
            gitaly_address: tcp://gitaly2.internal:8075
+           gitaly_token: AUTH_TOKEN_2
            path: /some/local/path
    ```