fix(gh-931): migrate fails on fresh cms

[wesleyboar]

Overview

Prevent failure of migration on a brand new CMS by running command on signal not migration.

Related

• fixes CMS Migration Fails on New CMS #931
• replaces docs(Core-CMS#931): workaround CMS migrate fail Core-Portal#1096
• required by feat: style editor & snippet user #940

Changes

• retires add_groups migration
• adds apps.py which creates groups
• adds dummy model so post_migrate signal fires

Testing

1. Set up a fresh CMS (no previous volumes):
   How to Setup CMS From Scratch? #942

2. In the output, after migrations, see log statement:

   Finished creating CMS groups

3. Open http://localhost:8000/admin/auth/group/.

4. Log in.

5. Verify groups exist.

6. Open http://localhost:8000/admin/auth/group/6/change/.

7. Verify permissions exist.

8. Re-run migrations

   docker exec -it core_cms python manage.py migrate
   

9. In the output, after "No migrations to apply.", see log statement:

   Finished updating CMS groups

UI

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[wesleyboar]

New Update to Testing Steps

Old Update to Testing Steps

I updated the terminal command to copy over the new Make commands:

git diff --name-only origin/feat/script-to-setup-cms..origin/main | xargs git restore --source=origin/feat/script-to-setup-cms --

^{Previous command relied on local branch. This command relies on remote branches.}

[wesleyboar]

Testing step prerequisite simplified as new issue #942.