[DAR-2463][External] Adjusted maximum number of items that can be registered in a single request

[JBWilkie]

Problem

Recently, we've encountered significant issues with our item processing queues being overloaded. Part of our strategy to mitigate this is to introduce rate limiting for the registration endpoints and a cap on the maximum number of items that can be registered in a single request. This PR introduces the latter for registration through darwin-py

Solution

Significantly reduce the maximum number of items that can be registered in a single request to 10

Changelog

Adjusted the maximum number of items that can be registered in a single request to 10 to reduce the chance of overloading our processing queues

[linear]

DAR-2463 Adjust number of items grouped into requests by darwin-py external storage bindings

[JBWilkie]

Closing since we haven't made this change on the BE, and we shouldn't introduce this into the SDK until the BE has been updated