新增：管理后台新增类型筛选

app/views/admins/users/index.html.erb

@@ -15,7 +15,11 @@
       <% identity_options = [['全部', ''], ['教师', 0], ['学生', 1], ['专业人士', 2]] %>
       <%= select_tag(:identity, options_for_select(identity_options), class: 'form-control') %>
     </div>
-
+    <div class="form-group mr-2">
+      <label for="identity">类型：</label>
+      <% open_user_type_options = [['所有用户', ''], ['头歌同步', "OpenUsers::Educoder"], ['平台注册', "Forge"],] %>
+      <%= select_tag(:open_user_type, options_for_select(open_user_type_options), class: 'form-control') %>
+    </div>
 
     <%= text_field_tag(:keyword, params[:keyword], class: 'form-control col-sm-2 ml-3', placeholder: 'ID/姓名/邮箱/手机号检索') %>