refactor(drm): resolve content keys in one licence path behind ServerKeySource

Drop null keys from every licence, server and export source, not only Widevine. dl now finds remote sessions and imports through ServerKeySource instead of private fields.

tests/remote/unit/test_server_cdm_max_height.py

@@ -13,6 +13,7 @@ import pywidevine.pssh as wv_pssh_mod
 from rich.table import Table
 
 import unshackle.core.drm as drm_mod
+from tests.remote.key_source import remote_keys
 from unshackle.commands.dl import dl
 from unshackle.core.api import handlers
 from unshackle.core.api.errors import APIError, APIErrorCode
@@ -203,16 +204,11 @@ _WV.__name__ = "Widevine"
 
 
 def remote(local_cdm, answer):
-    svc = RemoteService.__new__(RemoteService)
+    svc = remote_keys(server_cdm_type="playready", local_cdm=local_cdm)
     svc._track_alias = {}
     svc._title_alias = {}
-    svc._server_cdm = True
-    svc._server_cdm_type = "playready"
     svc._session_id = "sess"
-    svc.server_vault_keys = {}
-    svc.client_licensed = set()
     svc.log = logging.getLogger("test-server-cdm-cap")
-    svc.ctx = SimpleNamespace(obj=SimpleNamespace(cdm=local_cdm))
     posts: list = []
     svc.client = SimpleNamespace(post=lambda endpoint, payload, expect=(): posts.append(payload) or answer)
     svc.drain_server_logs = lambda: None
@@ -557,7 +553,7 @@ def prepare(svc, licence):
 
 
 def test_dl_licenses_a_client_licensed_track_with_the_local_device():
-    svc = SimpleNamespace(_server_cdm=True, client_licensed={"vid"}, local_cdm="local device")
+    svc = remote_keys(client_licensed={"vid"}, local_cdm="local device")
 
     server_calls: list = []
 
@@ -566,7 +562,7 @@ def test_dl_licenses_a_client_licensed_track_with_the_local_device():
 
 
 def test_dl_takes_the_local_path_when_the_server_hands_the_track_over():
-    svc = SimpleNamespace(_server_cdm=True, client_licensed=set(), local_cdm="local device")
+    svc = remote_keys(local_cdm="local device")
     assert prepare(svc, lambda **kwargs: svc.client_licensed.add("vid")) == "local device"
 
 
@@ -587,7 +583,7 @@ class PlayReady:
 def test_a_mid_download_handover_puts_the_keys_on_the_callers_drm(monkeypatch):
     """The caller decrypts with the DRM object it passed in, so the local licence must fill that one."""
     monkeypatch.setattr(dl, "LICENSE_KEY_CACHE", {})
-    svc = SimpleNamespace(_server_cdm=True, client_licensed=set(), local_cdm="local device", server_vault_keys={})
+    svc = remote_keys(local_cdm="local device")
     runner = dl.__new__(dl)
     runner._remote_service = svc
     runner.cdm = "server stub"