Defer the tags_list for media models

[obulat]

Fixes

Related to #704 by @obulat

Description

This is the first step of the three-step process we need to follow to remove the tags_list from the database for zero-downtime deployments. This PR adds a custom Manager to the AbstractMedia model that prevents querysets from trying to access tags_list field as part of the model.

After this PR is deployed, we will need to drop the tags_list column from the database.

After the column is dropped, we can deploy the PR #956 that removes the tags_list field from the models and adds corresponding migrations. Note: the CustomManager needs to be removed from #956, otherwise we get an error when it is trying to defer the tags_list field that doesn't exist.

Testing Instructions

Run just up and search for something (http://localhost:50280/v1/images/?q=cat). In the logs (run just logs web or use the Docker UI to view the openverse-web-1 logs), you should see a log line with SELECT query that does not have tags_list:

2023-03-26 21:04:00 [2023-03-26 18:04:00,636 - django.db.backends - 131][DEBUG] 
[5caaae77211340c0a6a0cd568d8e9ec3] (0.014) SELECT "image"."id", "image"."created_on", "image"."updated_on", "image"."identifier", "image"."foreign_identifier", "image"."title", "image"."foreign_landing_url", "image"."creator", "image"."creator_url", "image"."thumbnail", "image"."provider", "image"."url", "image"."filesize", "image"."filetype", "image"."watermarked", "image"."license", "image"."license_version", "image"."source", "image"."last_synced_with_source", "image"."removed_from_source", "image"."view_count", "image"."tags", "image"."category", "image"."meta_data", "image"."width", "image"."height", "api_matureimage"."created_on", "api_matureimage"."identifier" FROM "image" LEFT OUTER JOIN "api_matureimage" ON ("image"."identifier" = "api_matureimage"."identifier") WHERE "image"."identifier" IN (UUID('3b858852-67df-44e1-8d57-683991d3ec67'), ...)); alias=default

If you do the same on main, you should see that the query does contain tags_list (see logs in this comment)

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[github-actions]

Full-stack documentation: Ready

https://WordPress.github.io/openverse/_preview/1029

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[AetherUnbound]

LGTM! Just one suggestion regarding the name of the custom manager class, but that's non-blocking.

[sarayourfriend]

LGTM, but big +1 to Madison's suggestion for a clearer name for the manager.

I think you can drop the "custom" from the name as well: that fact is implied by its definition. (That's really just a nit though!)