Split tests into more unitary tests

[gfeun]

We have tests that are too big and general.
This means that when they fail it is not directly clear what is broken.

We should break those tests into smaller, more focused ones.

Exemple:

remote-key-server/tests/test/test_rks_administration_api.py

Line 79 in 3b16a4b

def test_create_group(self, admin_api):