Setup a test environnement

[CChemin]

For now, when writing a new universe package, we first push it on the master branch without testing. As it is not the best practice it would be better having a test branch associated to a test catalog.
The idea would be :

• having a test branch on InseeFrLab/Universe-Datascience
• changing the CI to generate a universe-test.json (where to put it ?)
• using universe-test.json in a "client" of Universe-Datascience (in our case it would consist in having onyxia-ui exposing a hidden test catalog)