[DAR-4304][External] Split annotation import payloads if required

[JBWilkie]

Problem

When importing annotations, if any single payload exceeds the maximum size allowed by the server, we'll get a RequestEntitySizeExceeded error and the import will stop

Solution

When we receive this error, we attempt to split the payload into multiple payloads, then import each one individually

Changelog

Ability to import very large annotation files - Those that would normally exceed our API limits

[linear]

DAR-4304 Manage big annotation import file