New 'deduplicationKey' parameter for the "Create batch" requests and changes to the "Delete batch" request

The deduplicationKey (UUID format) was added to the "Create batch request"; it's assigned during the creation via a query parameter. If a consecutive request is sent with the same ID, then we will reply with the memorized (for 1 hour) result for the first request.

Instead of a 404 error, we reply with deleteCount: 0 for batches that were requested to be deleted if they were already completed.