Use wsgi in k8s deployment

[jbagot]

Is your feature request related to a problem? Please describe.
The k8s manifest is using the migrate and runserver from django instead of a proper wsgi.

Describe the solution you'd like
We should use gunicorn or uwsgi. Already exist an invoke task called uwsgi that we can use in the manifest. Or if someone prefer gunicorn or another alternative you can add a invoke task and use it in the manifest.