新增课程成员时增加默认选项

app/views/courses/_course_members.html.erb

@@ -35,7 +35,7 @@
           </li>
           <% @roles.each do |role| %>
               <li>
-                <%= radio_button_tag 'membership[role_ids][]', role.id %>
+                <%= radio_button_tag 'membership[role_ids][]', role.id, role.name == "学生" || role.name == "Student" %>
                 <label ><%= h role %></label>
               </li>
           <% end %>