Optionally return status on WriteRelationships

authzed/api/v1/permission_service.proto

@@ -265,9 +265,41 @@ message WriteRelationshipsRequest {
   repeated Precondition optional_preconditions = 2
       [ (validate.rules).repeated .items.message.required =
             true ]; // To be bounded by configuration
+
+  // with_status, if true, indicates that the response should include the status of each update.
+  // This can be useful for knowing how to rollback a given call to WriteRelationships, but adds a small amount
+  // of compute overhead to the request.
+  bool with_status = 3;
 }
 
-message WriteRelationshipsResponse { ZedToken written_at = 1; }
+// RelationshipUpdateStatus is the status of a relationship update.
+message RelationshipUpdateStatus {
+  message Update {
+    // old is the previous relationship.
+    Relationship old = 1;
+    // new is the new relationship.
+    Relationship new = 2;
+  }
+
+  oneof status {
+    // no_op indicates that the relationship was not changed (already existed on TOUCH, or didn't exist on DELETE).
+    Relationship no_op = 1;
+    // created indicates that the relationship was created.
+    Relationship created = 2;
+    // deleted indicates that the relationship was deleted.
+    Relationship deleted = 3;
+    // updated indicates that the relationship was updated.
+    Update updated = 4;
+  }
+}
+
+message WriteRelationshipsResponse {
+  // written_at is the revision at which the relationships were written.
+  ZedToken written_at = 1;
+
+  // updates is the status of each relationship update, if requested.
+  repeated RelationshipUpdateStatus updates = 2;
+}
 
 // DeleteRelationshipsRequest specifies which Relationships should be deleted,
 // requesting the delete of *ALL* relationships that match the specified