Add Docker-executed pytest suite with >90% coverage

apps/newsletter/tests/test_more.py

@@ -0,0 +1,14 @@
+import pytest
+
+from apps.newsletter.services import ProviderSyncService
+from apps.newsletter.views import confirmation_token
+
+
+def test_confirmation_token_roundtrip():
+    token = confirmation_token("x@example.com")
+    assert token
+
+
+def test_provider_sync_not_implemented():
+    with pytest.raises(NotImplementedError):
+        ProviderSyncService().sync(None)