Configure dockerflow on NAU Richie for better healthcheck

[igobranco]

The dockerflow package is installed on Richie, but it isn't properly configured.

Dockerflow documentation: https://github.com/mozilla-services/python-dockerflow/blob/main/docs/django.rst

• https://www.nau.edu.pt/__heartbeat__/
• https://www.nau.edu.pt/__version__/
• https://www.nau.edu.pt/__lbheartbeat__/

Example, configure it like:

DOCKERFLOW_CHECKS = [
  "dockerflow.django.checks.check_redis_connected",
  "dockerflow.django.checks.check_database_connected",
]

Others dockerflow.django.checks.check_migrations_applied

Related to: #220

[igobranco]

The NAU Richie doesn't use the normal Redis cache, but another with a fallback. So this won't be possible to implement without removing the fallack.