api(materialize/v0): add affected relations to breaking schema change message

Author: ostafen

authzed/api/materialize/v0/watchpermissionsets.proto

@@ -192,6 +192,21 @@ message LookupPermissionSetsRequired {
 message BreakingSchemaChange {
   // change_at is the revision at which a breaking schema event has happened.
   authzed.api.v1.ZedToken change_at = 1;
+
+  // AffectedRelation represents a namespace#relation pair that was affected by the breaking schema change.
+  message AffectedRelation {
+    // namespace is the object type/resource type that was affected
+    string namespace = 1;
+
+    // relation is the relation or permission that was affected
+    string relation = 2;
+  }
+
+  // affected_relationships lists all the namespace#relation pairs that were directly affected by the breaking schema change.
+  repeated AffectedRelation affected_relations = 2;
+
+  // reason provides an optional human-readable description of what caused the breaking schema change.
+  string reason = 3;
 }
 
 message DownloadPermissionSetsRequest {