fix(specs): define batch actions (#5242)

Author: kai687

specs/common/schemas/Batch.yml

@@ -48,4 +48,19 @@ action:
     - deleteObject
     - delete
     - clear
-  description: Type of indexing operation.
+  description: |
+    Which indexing operation to perform:
+
+    - `addObject`: adds records to an index.
+       Equivalent to the "Add a new record (with auto-generated object ID)" operation.
+    - `updateObject`: adds or replaces records in an index.
+       Equivalent to the "Add or replace a record" operation.
+    - `partialUpdateObject`: adds or updates attributes within records.
+       Equivalent to the "Add or update attributes" operation with the `createIfNoExists` parameter set to true.
+       (If a record with the specified `objectID` doesn't exist in the specified index, this action creates adds the record to the index)
+    - `partialUpdateObjectNoCreate`: same as `partialUpdateObject`, but with `createIfNoExists` set to false.
+       (A record isn't added to the index if its `objectID` doesn't exist)
+    - `deleteObject`: delete records from an index.
+      Equivalent to the "Delete a record" operation.
+    - `delete`. Delete an index. Equivalent to the "Delete an index" operation.
+    - `clear`: delete all records from an index. Equivalent to the "Delete all records from an index operation".