Sped up artist enrichment at least somewhat

shanty-data/src/traits.rs

@@ -48,6 +48,12 @@ pub trait MetadataFetcher: Send + Sync {
         &self,
         artist_mbid: &str,
     ) -> impl Future<Output = DataResult<Vec<ReleaseGroupEntry>>> + Send;
+
+    /// Resolve a release-group MBID to a concrete release MBID (first release in the group).
+    fn resolve_release_from_group(
+        &self,
+        release_group_mbid: &str,
+    ) -> impl Future<Output = DataResult<String>> + Send;
 }
 
 /// Fetches artist image URLs from an external source.