Non-descriptive error for incorrect uuid

[DataGreed]

1. Send an event with custom uuid parameter set to something like "foo"
2. Get an error [PostHog] failed to parse request: data did not match any variant of untagged enum RawRequest (400)

I expected to see a more descriptive error, like "uuid field should be a valid UUID" or something like that. It's also kind of weird that the library doesn't properly check uuid field and lets any string through if it expects it to be in UUID format.

That would have saved me an hour of debugging.