Refresh including django, python and requirements

• Updated python to 3.9
• Updated django to 3.2
• Removed unnecessary requirements
  • automationcommon
  • ruamel.yaml
  • django-restframework
  • django-ucamwebauth (except for tox testing)
• mailhog only needed for production docker-compose
• /healthz -> /healthy
• general .gitignore, etc tweaks

Closes: #6 (closed)