Assign topics to videos and playlists

[mbertrand]

What are the relevant tickets?

Closes #579

Description (What does it do?)

For videos, runs an opensearch course query for each video to guesstimate the covered topics based on the video title & description fields, and assigns the 3 most common topics from the results. (Port of open-discussions functionality).
For video playlists, assigns the 3 most common topics from the videos in the playlist.

How can this be tested?

Follow testing instructions for PR #558. Everything should work the same, except that most video and video playlist resources should now have up to 3 topics assigned to them after the ETL pipeline is complete. This assumes you already have a decent amount of courses available with topics. If you don't, run ./manage.py backpopulate_ocw_data --skip-contentfiles first, it will likely take 20-30 minutes or so.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.26%. Comparing base (c48fa83) to head (2d3f970).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #584      +/-   ##
==========================================
+ Coverage   77.18%   77.26%   +0.07%     
==========================================
  Files         243      243              
  Lines       10525    10561      +36     
  Branches     1786     1793       +7     
==========================================
+ Hits         8124     8160      +36     
  Misses       2230     2230              
  Partials      171      171              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[abeglova]

The code looks fine. I have all the ocw courses in my local database, and the topic assignments were not very good. In particular it seemed quite bad for humanities videos. It seemed to assign the top topics( Probability and Statistics, Engineering, Computer Science, Business etc to everything)

[abeglova]

I'm not sure if expanding the columns that are used to make the assignments beyond title, course number and the descriptions would help. Attaching the course that the video came from to the video and getting the topics that way would be definitely better

[mbertrand]

I created a new issue to improve the video topics assignment: #594