chore: Refactor code to use SourceUpdater struct for managing sources

src/host/store/file-mappings.go

@@ -55,3 +55,7 @@ func (r *FilesMappings) FileMappings(ctx context.Context, ih infohash.T) (map[st
 	})
 	return out, err
 }
+
+func (r *FilesMappings) Close(ctx context.Context) error {
+	return r.mappings.Close(ctx)
+}