Sort by coursenums, filtering by department if applicable

[mbertrand]

What are the relevant tickets?

Closes #195

Description (What does it do?)

• Allows search results to be sorted by primary course number
• If there is a departments filter applied, sort by course numbers for that department
• Modifies LEARNING_RESOURCE_SORTBY_OPTIONS to be a dict that is used to provide more user-friendly sort options to the user. For example, the user can sort by mitcoursenumber and that will actually sort by course.course_numbers.sort_coursenum
• Adjusts the department filter so that it works by department id instead of name (ex: "CMS-W" instead of "Comparative Media Studies/Writing")

How can this be tested?

• Temporarily modify learning_resources_search.constants.SOURCE_EXCLUDED_FIELDS to be an empty list so you will be able to see the course.course_numbers.sort_coursenum values.

• Import a bunch of OCW courses, among them 21H.104J+fall_2010 and a few other courses with the department_id "11" (Urban Studies and Planning), plus some other departments.

  ./manage.py backpopulate_ocw_data --course-num 21h-104j-riots-strikes-and-conspiracies-in-american-history-fall-2010
  

• Go to this url to sort by course number, filtered by department:
  http://localhost:8063/api/v1/learning_resources_search/?department=11&sortby=mitcoursenumber

• Verify the results are in ascending order by course.course_numbers.sort_coursenum for the respective department ("11"). The course mentioned above, 21H.104J+fall_2010, has a cross-listed id within that department of "11.015J" so it should appear in the correct position relative to the other courses imported from that department.

• Go to this url to sort by course number, unfiltered by department:
  http://localhost:8063/api/v1/learning_resources_search/?sortby=mitcoursenumber

• Verify the results are sorted by course.course_numbers.sort_coursenum where listing_type=primary, and not by any cross-listed numbers.

• Check that the schema documentation for this endpoint shows some user-friendly sort options:

I did not try to make the departments parameter schema documentation more user-friendly in this PR, leaving that for a future one because the use of a custom field class (StringArrayField) for that parameter makes it seem at first glance that doing so might be somewhat involved.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9b919af) 76.79% compared to head (bc71b04) 76.81%.

Additional details and impacted files

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##             main     #197      +/-   ##
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+ Coverage   76.79%   76.81%   +0.02%     
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  Files         313      313              
  Lines       13645    13653       +8     
  Branches     2239     2243       +4     
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+ Hits        10478    10487       +9     
  Misses       2894     2894              
+ Partials      273      272       -1     

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[ChristopherChudzicki]

This is working as expected and looks good 👍

I’m also noticing a few possible ETL issues that seem unrelated to this work…

• https://mit-open-rc.odl.mit.edu/api/v1/courses/?platform=mitxonline&department=11 ... The course number is course-v1:MITxT+11.S952x. That seems like a readable_id to me. Should the course number just be 11.S952x?
  • Edit: Talked to Matt; this is expected right now.
• I notice that many of the course number fields in https://mit-open-rc.odl.mit.edu/api/v1/courses/?department=21H have department: null. Seems like it should be 21H?