Add fields to discussion thread list endpoint

This commit adds fields that are related to the requesting user's
interaction with the thread (e.g. following).

lms/djangoapps/discussion_api/api.py

@@ -14,6 +14,7 @@ from django_comment_common.models import (
     Role,
 )
 from lms.lib.comment_client.thread import Thread
+from lms.lib.comment_client.user import User
 from openedx.core.djangoapps.course_groups.cohorts import get_cohort_id
 
 
@@ -76,7 +77,7 @@ def get_course_topics(course, user):
     }
 
 
-def _cc_thread_to_api_thread(thread):
+def _cc_thread_to_api_thread(thread, cc_user):
     """
     Convert a thread data dict from the comment_client format (which is a direct
     representation of the format returned by the comments service) to the format
@@ -98,6 +99,10 @@ def _cc_thread_to_api_thread(thread):
     ret.update({
         "topic_id": thread["commentable_id"],
         "raw_body": thread["body"],
+        "following": thread["id"] in cc_user["subscribed_thread_ids"],
+        "abuse_flagged": cc_user["id"] in thread["abuse_flaggers"],
+        "voted": thread["id"] in cc_user["upvoted_ids"],
+        "vote_count": thread["votes"]["up_count"],
         "comment_count": thread["comments_count"],
         "unread_comment_count": thread["unread_comments_count"],
     })
@@ -125,6 +130,7 @@ def get_thread_list(request, course_key, page, page_size):
         name__in=[FORUM_ROLE_ADMINISTRATOR, FORUM_ROLE_MODERATOR, FORUM_ROLE_COMMUNITY_TA],
         users=request.user
     ).exists()
+    cc_user = User.from_django_user(request.user).retrieve()
     threads, result_page, num_pages, _ = Thread.search({
         "course_id": unicode(course_key),
         "group_id": None if user_is_privileged else get_cohort_id(request.user, course_key),
@@ -139,5 +145,5 @@ def get_thread_list(request, course_key, page, page_size):
     if result_page != page:
         raise Http404
 
-    results = [_cc_thread_to_api_thread(thread) for thread in threads]
+    results = [_cc_thread_to_api_thread(thread, cc_user) for thread in threads]
     return get_paginated_data(request, results, page, num_pages)