调整开通身份

modules/User/Http/Resources/IdentityMiddleResource.php

@@ -19,7 +19,7 @@ class IdentityMiddleResource extends JsonResource
         return [
             'name'       => $this->identity->name,
             'serial'     => $this->identity->serial_prefix.$this->serial,
-            'started_at' => $this->started_at ?? '',
+            'started_at' => (string)$this->started_at ?? '',
             'ended_at'   => $ended_at,
         ];
     }