feat(domain): add actor_json to FederationActionPort

crates/domain/src/testing.rs

@@ -547,6 +547,10 @@ impl FederationActionPort for TestStore {
     ) -> Result<(), DomainError> {
         Ok(())
     }
+
+    async fn actor_json(&self, _user_id: &UserId) -> Result<String, DomainError> {
+        Err(DomainError::NotFound)
+    }
 }
 
 #[async_trait]
@@ -806,6 +810,13 @@ mod federation_port_tests {
             .await
             .unwrap();
     }
+
+    #[tokio::test]
+    async fn test_store_actor_json_returns_not_found() {
+        let store = TestStore::default();
+        let err = store.actor_json(&UserId::new()).await.unwrap_err();
+        assert!(matches!(err, DomainError::NotFound));
+    }
 }
 
 #[cfg(test)]