feat(capture): handle empty string UUIDs for /batch endpoint

[dmarticus]

Problem

We tried to make a change to the Go SDK to support passing in client-defined UUIDs to the /batch endpoint, but sometimes those UUIDs were empty strings. This led to the SDK breaking because, while our batch endpoint supports passing in UUIDs, it doesn't handle the empty string case. Obviously, we should tell our users to omit UUIDs that are empty, but I think updating our serializer to ignore them is probably a good idea, too.

Changes

Update the RawEvent serializer to treat empty strings in the UUID field as None.

Does this work well for both Cloud and self-hosted?

Yup.

How did you test this code?

Wrote some tests; maybe overkill, but still seems handy since this is a non-standard deserialization path. Here's a rust playground that shows the fix, too: https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=648f9a409cd5c89fdbc4b05c786d5b3a

[oliverb123]

+1, we need to handle this edge case as customer reports python capture supports it