Updates to artist credit handling

src/queries/cache.rs

@@ -63,3 +63,12 @@ pub async fn purge_expired(db: &DatabaseConnection) -> DbResult<u64> {
         .await?;
     Ok(result.rows_affected)
 }
+
+/// Delete all cache entries whose key starts with the given prefix.
+pub async fn purge_prefix(db: &DatabaseConnection, prefix: &str) -> DbResult<u64> {
+    let result = SearchCache::delete_many()
+        .filter(search_cache::Column::QueryKey.starts_with(prefix))
+        .exec(db)
+        .await?;
+    Ok(result.rows_affected)
+}