修改api调用方法

docs/user_api.rst

@@ -11,7 +11,7 @@ API 文档
 
 ::
 
-    $ curl -X POST -F username=admin -F password=admin http://localhost/api/users/v1/token/  # 获取token
+    $ curl -X POST -H 'Content-Type: application/json' -d '{"username": "admin", "password": "admin"}' http://localhost/api/users/v1/token/  # 获取token
     {"Token":"937b38011acf499eb474e2fecb424ab3","KeyWord":"Bearer"}%  # 获取到的token
 
     $ curl -H 'Authorization: Bearer 937b38011acf499eb474e2fecb424ab3' -H "Content-Type:application/json" http://localhost/api/users/v1/users/