Removed user choice field from browseable catalog API pages

The viewers field attempts to render all users in the system. This does not scale and may bring down the system. This fix renders the field as a text input.

ECOM-5964

course_discovery/apps/api/serializers.py

@@ -292,7 +292,8 @@ class CatalogSerializer(serializers.ModelSerializer):
     courses_count = serializers.IntegerField(read_only=True, help_text=_('Number of courses contained in this catalog'))
     viewers = serializers.SlugRelatedField(slug_field='username', queryset=User.objects.all(), many=True,
                                            allow_null=True, allow_empty=True, required=False,
-                                           help_text=_('Usernames of users with explicit access to view this catalog'))
+                                           help_text=_('Usernames of users with explicit access to view this catalog'),
+                                           style={'base_template': 'input.html'})
 
     def create(self, validated_data):
         viewers = validated_data.pop('viewers')