Implement argo to compute density map

>@afonsobspinto herewith my thoughts about how to do this:

we use argo for running the generate image(s) task
we add a status to population to represent the status of the image(s) generation (also add an error status for when things fails)
create a django management command (https://docs.djangoproject.com/en/3.2/howto/custom-management-commands/) to execute the generation of the images
create a workflow task docker image in the workspaces application
create a submit argo workflow task (use cloudharness library for this, there is already something like this)
(we can create a task per population or per population per subdivision, imo it's per population because imo the generation of the images per population is an atomic operation)
I know in future this might change when we are going to upload the keys and values files. But then we already have the "framework" and can easily adapt it to match/work with the new file stucture(s).