Implement batch operations feature #790
Description
Implement batch operations feature as described in the specification:
https://github.com/ably/docs/blob/main/content/client-lib-development-guide/features.textile#batch-operations
For reference please see: https://ably.com/docs/rest/batch
The original PR for spec creation: ably/docs#1421
Acceptance criteria: feature has been implemented and unit test has been written.
┆Issue is synchronized with this Jira Story by Unito