feat(campaigns): add governed collaboration thread

tests/test_access_provider.py

@@ -21,6 +21,7 @@ from govoplan_campaign.backend.db.models import (
     AttachmentBlob,
     AttachmentInstance,
     Campaign,
+    CampaignCollaborationEntry,
     CampaignIssue,
     CampaignJob,
     CampaignMessageAction,
@@ -46,6 +47,61 @@ GROUP_ID = "group-1"
 
 
 class CampaignAccessProviderTests(unittest.TestCase):
+    def test_collaboration_access_is_explained_independently_from_campaign_edit(self) -> None:
+        session = _session()
+        self.addCleanup(_close_session, session)
+        _seed_access_subjects(session)
+        campaign = Campaign(
+            id="campaign-collaboration",
+            tenant_id=TENANT_ID,
+            owner_user_id=OTHER_USER_ID,
+            external_id="collaboration",
+            name="Collaboration campaign",
+        )
+        entry = CampaignCollaborationEntry(
+            id="discussion-1",
+            tenant_id=TENANT_ID,
+            campaign_id=campaign.id,
+            actor_user_id=OTHER_USER_ID,
+            actor_label_snapshot="Other user",
+            visibility="collaborators",
+            content="Not disclosed by provenance",
+            content_sha256="a" * 64,
+        )
+        session.add_all(
+            [
+                campaign,
+                entry,
+                CampaignShare(
+                    id="share-collaboration",
+                    tenant_id=TENANT_ID,
+                    campaign_id=campaign.id,
+                    target_type="group",
+                    target_id=GROUP_ID,
+                    permission="read",
+                ),
+            ]
+        )
+        session.commit()
+
+        items = CampaignAccessService().explain_resource_provenance(
+            session,
+            _principal(
+                scopes={"campaigns:campaign:read", "campaigns:discussion:post"},
+                group_ids={GROUP_ID},
+            ),
+            resource_type="campaign_collaboration_entry",
+            resource_id=entry.id,
+            action="campaigns:discussion:post",
+        )
+
+        discussion = next(item for item in items if item.source == "campaigns.collaboration_entry")
+        self.assertEqual(["campaigns:discussion:post"], discussion.details["permission_actions"])
+        self.assertFalse(discussion.details["content_disclosed"])
+        self.assertTrue(any(item.id == "share-collaboration" for item in items))
+        self.assertNotIn("campaigns:campaign:update", repr(discussion.details))
+        self.assertNotIn("Not disclosed", repr(items))
+
     def test_campaign_access_provider_explains_owner_share_admin_and_missing_resources(self) -> None:
         session = _session()
         self.addCleanup(_close_session, session)
@@ -918,6 +974,7 @@ def _session():
             Group.__table__,
             Campaign.__table__,
             CampaignShare.__table__,
+            CampaignCollaborationEntry.__table__,
             CampaignVersion.__table__,
             CampaignJob.__table__,
             CampaignIssue.__table__,