Clean ID of course_module for push notification channel name.

Update Mobile API to include channel_id for course.

common/lib/xmodule/xmodule/course_module.py

@@ -10,6 +10,7 @@ import requests
 from datetime import datetime
 import dateutil.parser
 from lazy import lazy
+from base64 import b32encode
 
 from xmodule.exceptions import UndefinedContext
 from xmodule.seq_module import SequenceDescriptor, SequenceModule
@@ -1398,3 +1399,12 @@ class CourseDescriptor(CourseFields, SequenceDescriptor):
             self.video_upload_pipeline is not None and
             'course_video_upload_token' in self.video_upload_pipeline
         )
+
+    def clean_id(self, padding_char='='):
+        """
+        Returns a unique deterministic base32-encoded ID for the course.
+        The optional padding_char parameter allows you to override the "=" character used for padding.
+        """
+        return "course_{}".format(
+            b32encode(unicode(self.location.course_key)).replace('=', padding_char)
+        )

lms/djangoapps/mobile_api/users/serializers.py

@@ -60,6 +60,7 @@ class CourseField(serializers.RelatedField):
             "course_updates": course_updates_url,
             "course_handouts": course_handouts_url,
             "course_about": course_about_url,
+            "subscription_id": course.clean_id(padding_char='_'),
         }
 
 

lms/djangoapps/mobile_api/users/tests.py

@@ -60,6 +60,7 @@ class TestUserEnrollmentApi(MobileAPITestCase, MobileAuthUserTestMixin, MobileEn
         self.assertTrue('course_handouts' in found_course)
         self.assertEqual(found_course['id'], unicode(self.course.id))
         self.assertEqual(courses[0]['mode'], 'honor')
+        self.assertEqual(courses[0]['course']['subscription_id'], self.course.clean_id(padding_char='_'))
 
     def verify_failure(self, response):
         self.assertEqual(response.status_code, 200)

lms/djangoapps/mobile_api/users/views.py

@@ -221,6 +221,7 @@ class UserCourseEnrollmentsList(generics.ListAPIView):
           * video_outline: The URI to get the list of all vides the user can
             access in the course.
           * id: The unique ID of the course.
+          * subscription_id: A unique "clean" (alphanumeric with '_') ID of the course.
           * latest_updates:  Reserved for future use.
           * end: The end date of the course.
           * name: The name of the course.