Add tests against actual quetz

[simonbohnen]

By SimonBohnenQC, copied from other repo.

SimonBohnenQC: We're currently not testing against live quetz, right? This would probably be something nice to have.

SimonBohnenQC: It looks to me like the mocked tests are also not reflecting the actual responses given by quetz. Consider the /api/channels/{channel_name}/members route. The mocked tests use the following json scheme:

quetz-client/tests/conftest.py

Lines 113 to 115 in 2765d57

	@pytest.fixture
	def expected_channel_members():
	return [{"username": "u1", "role": "owner"}, {"username": "u2", "role": "member"}]

Whereas actual quetz specifies the following scheme:

[
  {
    "role": "member",
    "user": {
      "id": "3fa85f64-5717-4562-b3fc-2c963f66afa6",
      "username": "string",
      "profile": {
        "name": "string",
        "avatar_url": "string"
      }
    }
  }
]

(You can find it in the Swagger docs when launching quetz)

JanJaguschQC: I had the same thought today when reviewing your PR. I like the idea. Testing against an actual Quetz instance shouldn't be too complicated, either.