Remove student self-unenrollment

The ability for students to unenroll themselves from a course turned out
to be an undesired feature. Therefore this commit disables it. UI
elements have been commented out, the /enroll/ URL has been commented
out, and the DELETE operation on the course students API view is now
only available for course staff.

course/api/views.py

@@ -147,12 +147,11 @@ class CourseStudentsViewSet(NestedViewSetMixin,
         returns the details of the current user.
 
     `DELETE /courses/<course_id>/students/<user_id>/`:
-        removes the enrollment.
+        removes the enrollment. Students cannot unenroll themselves.
 
     - URL parameters:
         - `status`: the new status for the enrollment. `REMOVED` and `BANNED`
-            are currently supported. Students can only remove (not ban)
-            themselves.
+            are currently supported.
     """
     permission_classes = api_settings.DEFAULT_PERMISSION_CLASSES + [
         IsCourseAdminOrUserObjIsSelf,
@@ -171,6 +170,13 @@ def get_queryset(self):
         return self.instance.students
 
     def destroy(self, request, *args, **kwargs):
+        if not self.is_course_staff:
+            return Response(
+                'Student self-unenrollment is not allowed. Contact course '
+                'staff if you wish to remove your enrollment.',
+                status=status.HTTP_403_FORBIDDEN
+            )
+
         status_arg = self.request.GET.get('status')
         if status_arg not in Enrollment.ENROLLMENT_STATUS.keys():
             return Response(
@@ -184,11 +190,11 @@ def destroy(self, request, *args, **kwargs):
                 'Enrollments cannot be activated via this API',
                 status=status.HTTP_400_BAD_REQUEST
             )
-        if status_code != Enrollment.ENROLLMENT_STATUS.REMOVED and not self.is_course_staff:
-            return Response(
-                'Students can only unenroll themselves (status=REMOVED) via this API',
-                status=status.HTTP_403_FORBIDDEN
-            )
+        # if status_code != Enrollment.ENROLLMENT_STATUS.REMOVED and not self.is_course_staff:
+        #     return Response(
+        #         'Students can only unenroll themselves (status=REMOVED) via this API',
+        #         status=status.HTTP_403_FORBIDDEN
+        #     )
 
         user = self.get_object().user
         enrollment = self.instance.get_enrollment_for(user)

course/long_urls.py

@@ -8,9 +8,9 @@
     url(USER_URL_PREFIX + r'enroll/$',
         views.Enroll.as_view(),
         name='enroll'),
-    url(USER_URL_PREFIX + r'unenroll/$',
-        views.Unenroll.as_view(),
-        name='unenroll'),
+    # url(USER_URL_PREFIX + r'unenroll/$',
+    #     views.Unenroll.as_view(),
+    #     name='unenroll'),
     url(USER_URL_PREFIX + r'setlang',
         views.LanguageView.as_view(),
         name="set-enrollment-language"),

course/templates/course/_course_menu.html

@@ -211,6 +211,7 @@ <h4>{{ group.label|parse_localization }}</h4>
 
 {% endif %}
 
+{% comment %}
 {% if is_student %}
 <li class="header">
 	<h4>{% trans "ENROLLMENT" %}</h4>
@@ -222,3 +223,4 @@ <h4>{% trans "ENROLLMENT" %}</h4>
 	</a>
 </li>
 {% endif %}
+{% endcomment %}

course/templates/course/course_base.html

@@ -146,6 +146,7 @@ <h4>{% trans "Calendar" %}</h4>
 	</div>
 </div>
 
+{% comment %}
 <div id="unenroll-modal" class="modal" tabindex="-1" role="dialog" aria-labelledby="unenroll-modal-title">
 	<div class="modal-dialog" role="document">
 	  <div class="modal-content">
@@ -189,6 +190,7 @@ <h4 class="modal-title" id="unenroll-modal-title">
 	  </div>
 	</div>
 </div>
+{% endcomment %}
 {% endblock %}
 
 {% block mobilemenu %}