Fixing double json encoding

src/Entity/GoogleApiServiceClient.php

@@ -205,7 +205,10 @@ class GoogleApiServiceClient extends ConfigEntityBase implements GoogleApiServic
    * {@inheritdoc}
    */
   public function setAuthConfig($config) {
-    return $this->auth_config = Json::encode($config);
+    if (is_array($config)) {
+      $config = Json::encode($config);
+    }
+    return $this->auth_config = $config;
   }
 
   /**