FeedIterator Diagnostics: Provide ability to determine LeaseToken along with batches

Is your feature request related to a problem? Please describe. Regardless of the configuration being applied, being able to see which ranges are being serviced (in terms of physical rangeids) is critical for troubleshooting feed performance.

While simply logging the value (received 100 items from Range 4) is one use it might be applied to, in some cases, it can be useful for internal routing prioritization too - i.e. “ok we’ll stuff something into the log deep down” does not address the need in full.

Describe the solution you’d like The callback that delivers a set of feed items should in some way convey the range id, as the V2 one did.

Describe alternatives you’ve considered I’m not aware of any way to determine where a batch of items came from

Additional context This is to some degree a restatement of items covered in #616, prompted by #1117. While I like the new APIs, not having this is a deal breaker for moving applications onto any SDK newer than V2, which is a major concern for me.

[ealsur]

Awesome! Glad to be on the same page 😄

Would it be ok to change the title to something like “Supply LeaseToken…” otherwise RangeId would lead to the ask being wrongly interpreted as needing the partition information (that was my initial interpretation).

[bartelink]

related: https://github.com/Azure/azure-cosmos-dotnet-v3/issues/400