make the ratingkeys work with multiple at once

src/paths/library/metadata/[ratingKey]/get-media-meta-data.yaml

@@ -3,15 +3,17 @@ get:
     - Library
   summary: Get Media Metadata
   description: |
-    This endpoint will return all the (meta)data of a library item specified with by the ratingKey.
+    This endpoint will return all the (meta)data of one or more library items specified by the ratingKey.
+    Multiple rating keys can be provided as a comma-separated list (e.g., "21119,21617").
   operationId: get-media-meta-data
   parameters:
     - name: ratingKey
       in: path
-      description: the id of the library item to return the children of.
+      description: The id(s) of the library item(s) to return metadata for. Can be a single ID or comma-separated list of IDs.
       schema:
-        type: integer
-        example: 9518
+        type: string
+        pattern: '^[0-9]+(,[0-9]+)*$'
+        example: "21119,21617"
       required: true
     - name: includeConcerts
       in: query