修复若干bug，优化若干代码

apps/enroll/urls.py

@@ -4,7 +4,7 @@ from . import views
 # from rest_framework.routers import DefaultRouter
 
 urlpatterns = [
-    path("department_cn/", views.DepartmentMessageView.as_view()),
+    path("department/", views.DepartmentMessageView.as_view()),
     path("sign_up/", views.SignUpView.as_view()),
     path("sign_up/verification_code/", views.SendEmailView.as_view()),
     # path("sign_up/<string:pk>", views.Sign_in.as_view({"get": "get"}))