Protect foreign key constraint between imagelist_images and imagelist

[dhruvkb]

Description

Since migration 0002 changes the primary key on the ImageList model, it breaks the foreign key constraint that refers to that column. This PR merges 0002 into 0001 so that the constraint is set after the changes to the primary key.

Credits to @AetherUnbound for pointing this bug out in prod.

Testing Instructions

1. Migrate the database

   docker-compose exec -T web python manage.py migrate

2. Describe the imagelist_images table.

   docker-compose exec -T db psql -U deploy -d openledger <<-EOF
   \d+ imagelist_images;
   EOF

3. Ensure 2 foreign key constraints:
   • FOREIGN KEY (image_id) REFERENCES image(id)
   • FOREIGN KEY (imagelist_id) REFERENCES imagelist(id)

⚠️ Production notice

Since 0002 is already a performed migration, removing the corresponding file might interfere with rollbacks etc. To prevent potential future problems, remove the entry from the django_migrations table.

DELETE FROM 
  django_migrations
WHERE
  app = 'api' 
  AND name = '0002_auto_20180723_1737';

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
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• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.

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[sarayourfriend]

Is there any way to fix this that doesn't involve changing the migration history? If not this LGTM but I think leaving the migration history as immutable is preferrable to modifying it.

Also if we go with this then let's go ahead and use the full name of the migration rather than an abbreviation when we run that script in prod.

[zackkrida]

Thank you @dhruvkb and @AetherUnbound, this is great.

[krysal]

Django has a command for squashing migrations, didn't it work here? Altering the old ones manually is not a good practice. Otherwise, it seems to work well.

[dhruvkb]

@krysal the reason I did not squash the migrations and rather edit them by hand was that this approach removes the need to actually run any migrations in production.

Editing migrations is bad but, in our case, the prod environment and dev are quite out of sync so the usual guidelines need to be bent a little to bring all environments to the same level again.

[AetherUnbound]

This migration ran successfully on a snapshot of prod ✔️