- instead of copying the code into the image, use a volume to install
  the code. That way if the code changes, there's no need to rebuild
  the image
- add .dockerignore
- modify docker-compose.yml to configure gnunet from a volume and have
  all gnunet data as a volume too
- test the images in the CI in a different job

with the current REST API, which it was proposed to be used in the
mixnet.

they were resturned the opposite they said to return.

- replace True asserts by the specific type
- stop re-creating REST objects in succesive test
- complete tests with assertions

`requests.post` data argument is used to send that in the **body** request,
not as json header.
The json argument can be a dictionary and doesn't need to be converted to
string.

and improve test assertions

to better show what they do

- remove the article
- separate words by undersore
- add adjetive

so that there's no need to build the whole URL every time.
Also:
- stop converting back and forth dictionaries and json strings
- rename response to r
- return tuples when there's an error to know the error
- use inline if

and set comment as docstring.

ie. the python code and docker that is only for the GNUnet REST API and
not the docker for building a GNUnet docker image.

Squasing all nkls' commits and appling juga's MR:
https://gitlab.com/nkls_pep/gnunet-docker/-/merge_requests/1