Add system tests

## Description

There should be a way to automatically test the Python SDK in a real container with a working Ankaios cluster. Having this, we should be able to minimize the problems that might appear during development and corner cases that are not tested correctly in the moment. The software tests should also be mandatory to run on every PR, to be sure that the functionality of the SDK is no affected.

## Goals

Software tests are implemented and are testing at least once all of the methods of the Ankaios class that communicate with the Ankaios cluster.

## Final result

### Summary

**To be filled when the final solution is sketched.**

### Tasks

- [ ] Investigate a way to implement software tests.
- [ ] Investigate what cases should be tested with software tests.
- [ ] Implement software tests.
- [ ] Add the software tests to GitHub actions.

No se especifica ningún archivo ni punto de entrada de pruebas. Empieza por identificar los métodos de la clase Ankaios del Python SDK que se comunican con un clúster de Ankaios en funcionamiento y, después, investiga cómo ejecutarlos en un contenedor real y en GitHub Actions. Se considera terminado cuando cada uno de esos métodos se ha probado al menos una vez y las pruebas del sistema se ejecutan en cada pull request.

Escrito por el modelo de indexación a partir del texto del issue.