feat(domain): FederationActionPort trait + avatar_url on RemoteActor

crates/domain/src/errors.rs

@@ -12,6 +12,8 @@ pub enum DomainError {
     Conflict(String),
     #[error("invalid input: {0}")]
     InvalidInput(String),
+    #[error("external service error: {0}")]
+    ExternalService(String),
     #[error("internal error: {0}")]
     Internal(String),
 }

crates/domain/src/models/remote_actor.rs

@@ -8,5 +8,6 @@ pub struct RemoteActor {
     pub inbox_url: String,
     pub shared_inbox_url: Option<String>,
     pub public_key: String,
+    pub avatar_url: Option<String>,
     pub last_fetched_at: DateTime<Utc>,
 }

crates/domain/src/ports.rs

@@ -194,6 +194,12 @@ pub trait RemoteActorRepository: Send + Sync {
     async fn find_by_url(&self, url: &str) -> Result<Option<RemoteActor>, DomainError>;
 }
 
+#[async_trait]
+pub trait FederationActionPort: Send + Sync {
+    async fn lookup_actor(&self, handle: &str) -> Result<RemoteActor, DomainError>;
+    async fn follow_remote(&self, local_user_id: &UserId, handle: &str) -> Result<(), DomainError>;
+}
+
 #[async_trait]
 pub trait FeedRepository: Send + Sync {
     async fn home_feed(

crates/domain/src/testing.rs

@@ -534,6 +534,21 @@ impl RemoteActorRepository for TestStore {
     }
 }
 
+#[async_trait]
+impl FederationActionPort for TestStore {
+    async fn lookup_actor(&self, _handle: &str) -> Result<RemoteActor, DomainError> {
+        Err(DomainError::NotFound)
+    }
+
+    async fn follow_remote(
+        &self,
+        _local_user_id: &UserId,
+        _handle: &str,
+    ) -> Result<(), DomainError> {
+        Ok(())
+    }
+}
+
 #[async_trait]
 impl FeedRepository for TestStore {
     async fn home_feed(
@@ -767,6 +782,32 @@ mod ap_repo_tests {
     }
 }
 
+#[cfg(test)]
+mod federation_port_tests {
+    use super::*;
+    use crate::value_objects::UserId;
+
+    fn uid() -> UserId {
+        UserId::new()
+    }
+
+    #[tokio::test]
+    async fn test_store_lookup_returns_not_found() {
+        let store = TestStore::default();
+        let err = store.lookup_actor("@alice@example.com").await.unwrap_err();
+        assert!(matches!(err, DomainError::NotFound));
+    }
+
+    #[tokio::test]
+    async fn test_store_follow_remote_is_noop_ok() {
+        let store = TestStore::default();
+        store
+            .follow_remote(&uid(), "@alice@example.com")
+            .await
+            .unwrap();
+    }
+}
+
 #[cfg(test)]
 mod search_tests {
     use super::*;