Django CI on GitHub Actions

Tests wait on a database container and run on a single core.

Why it happens

A service container starts cold each run and Django's test runner is serial by default.

What to change

1. Run tests with --parallel auto to fork across every core
2. Use --keepdb so migrations are not replayed on every run
3. Cache the virtualenv and use uv for install
4. Start Postgres as a service container with a tmpfs data directory

Django on runnerhut

jobs:
  test:
    runs-on: runnerhut-8vcpu-ubuntu-2404
    services:
      postgres:
        image: postgres:17
        env: { POSTGRES_PASSWORD: postgres }
        options: >-
          --health-cmd pg_isready --health-interval 5s
    steps:
      - uses: actions/checkout@v4
      - run: uv sync --frozen
      - run: uv run python manage.py test --parallel auto --keepdb

The only runnerhut-specific line is `runs-on: runnerhut-8vcpu-ubuntu-2404`. Everything else is standard GitHub Actions — the same actions, the same secrets and the same permissions model you use today.