Add developer guide #42

	---
	name: test_code

	on:
	push:
	branches: [dev]
	pull_request:
	branches: [dev]

	jobs:
	test_core:
	runs-on: ['ubuntu-latest']
	steps:
	- uses: actions/checkout@v3
	- name: Login to GitHub Packages
	uses: docker/login-action@v1
	with:
	registry: docker.pkg.github.com
	username: ${{ github.actor }}
	password: ${{ secrets.GH_TOKEN }}
	- name: Pull and run Docker image
	run: \|
	docker pull docker.pkg.github.com/seshat-global-history-databank/seshat/tests-image:latest
	docker run -d -p 5432:5432 -v ${{ github.workspace }}:/seshat -e DJANGO_SETTINGS_MODULE=seshat.settings.local -e POSTGRES_PASSWORD=postgres -e PGDATA=/var/lib/postgresql/data/db-files/ -e GITHUB_ACTIONS='true' --name seshat_testing docker.pkg.github.com/seshat-global-history-databank/seshat/tests-image:latest
	- name: Sleep, then check PostgreSQL connectivity
	run: \|
	sleep 10
	docker exec seshat_testing psql -h localhost -U postgres -c 'SELECT 1'
	- name: Run tests
	run: \|
	docker exec seshat_testing python3 /seshat/manage.py test seshat.apps.core

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