AA-722: surface num_droppable assignments in MFE Progress Tab API

lms/djangoapps/course_home_api/progress/v1/serializers.py

@@ -53,6 +53,7 @@ class GradingPolicySerializer(serializers.Serializer):
 
     def get_assignment_policies(self, grading_policy):
         return [{
+            'num_droppable': assignment_policy['drop_count'],
             'type': assignment_policy['type'],
             'weight': assignment_policy['weight'],
         } for assignment_policy in grading_policy['GRADER']]

lms/djangoapps/course_home_api/progress/v1/views.py

@@ -68,6 +68,7 @@ class ProgressTabView(RetrieveAPIView):
         enrollment_mode: (str) a str representing the enrollment the user has ('audit', 'verified', ...)
         grading_policy:
             assignment_policies: List of serialized assignment grading policy objects, each has the following fields:
+                num_droppable: (int) the number of assignments able to be dropped
                 type: (str) the assignment type
                 weight: (float) the percent weight the given assigment type has on the overall grade
             grade_range: an object containing the grade range cutoffs. The exact keys in the object can vary, but they