Add LearningResource.delivery field (eventually to replace learning_format)

[mbertrand]

What are the relevant tickets?

Partially addresses https://github.com/mitodl/hq/issues/5126

Description (What does it do?)

• Adds a delivery field to LearningResource with a default value the same as for learning_format
• Modifies the OCW and Sloan ETL pipelines to populate the values correctly. The default value is fine for all other sources.
• Updates the search index to include the delivery field.

How can this be tested?

• Ingest these OCW courses if you haven't done so already - you'll need to assign OCW_ env settings to the same as RC.

./manage.py backpopulate_ocw_data --course-name 16-810-engineering-design-and-rapid-prototyping-january-iap-2007 --skip-contentfiles
./manage.py backpopulate_ocw_data --course-name res-7-006-7-03x-genetics --skip-contentfiles

)

• Run docker compose up, the new migration should complete.
• Check that the 16.810 course has a delivery value of ["online", "offline"], while the 7.006 course has a value of just ["online"]
• You can run the mgmt commands again, though this will temporarily make 7.006 include "offline" too until Include hide_download in data.json ocw-hugo-themes#1445 is merged and a mass publish is run.

Additional Context

The learning_format field is not removed in this PR because doing so would cause complications with several related repos (course-search-utils, open-api-clients). After both of these repos are updated to include delivery, then learning_format can be removed, and the front end can be updated to use delivery instead.

[abeglova]

Looks like you started to add delivery to the search api but did not finish. Other than that, works great

[abeglova]

Search aggregated by delivery does not work RN you need to add "delivery": FilterConfig("delivery.code"), to SEARCH_FILTERS in learning_resource_search/constants.py for delivery to be a valid aggregation option.

Additionally you should add delivery to LearningResourcesSearchRequestSerializer