Add indexed has_enrollable_seats field to CourseRun model.

This field will make it possible for clients of the search/all
endpoint to filter CourseRun results to those that have enrollable
seats.

ENT-687

course_discovery/apps/api/serializers.py

@@ -56,7 +56,7 @@ COURSE_RUN_SEARCH_FIELDS = (
     'enrollment_end', 'pacing_type', 'language', 'transcript_languages', 'marketing_url', 'content_type', 'org',
     'number', 'seat_types', 'image_url', 'type', 'level_type', 'availability', 'published', 'partner', 'program_types',
     'authoring_organization_uuids', 'subject_uuids', 'staff_uuids', 'mobile_available', 'logo_image_urls',
-    'aggregation_key', 'min_effort', 'max_effort', 'weeks_to_complete',
+    'aggregation_key', 'min_effort', 'max_effort', 'weeks_to_complete', 'has_enrollable_seats',
 )
 
 PROGRAM_FACET_FIELD_OPTIONS = {

course_discovery/apps/course_metadata/models.py

@@ -495,6 +495,14 @@ class CourseRun(TimeStampedModel):
 
         return deadline
 
+    @cached_property
+    def has_enrollable_seats(self):
+        """
+        Return a boolean indicating whether or not enrollable Seats are available for this CourseRun.
+        """
+        seat_types = [choice[0] for choice in Seat.SEAT_TYPE_CHOICES]
+        return len(self.enrollable_seats(seat_types)[:1]) > 0
+
     def enrollable_seats(self, types):
         """
         Returns seats, of the given type(s), that can be enrolled in/purchased.

course_discovery/apps/course_metadata/search_indexes.py

@@ -170,6 +170,7 @@ class CourseRunIndex(BaseCourseIndex, indexes.Indexable):
     has_enrollable_paid_seats = indexes.BooleanField(null=False)
     paid_seat_enrollment_end = indexes.DateTimeField(null=True)
     license = indexes.MultiValueField(model_attr='license', faceted=True)
+    has_enrollable_seats = indexes.BooleanField(model_attr='has_enrollable_seats', null=False)
 
     def prepare_aggregation_key(self, obj):
         # Aggregate CourseRuns by Course key since that is how we plan to dedup CourseRuns on the marketing site.