Fix support for Rust SentrySDK

I've had a quick go at the rust sample app provided (https://gitlab.com/eminence/test-sentry-project)

[sentry] enabled sentry client for DSN ...
[sentry] Get response: ``
[sentry] Get response: ``
[sentry] Get response: ``
[sentry] Get response: ``
thread 'main' panicked at 'test panic', src/main.rs:36:5

The panic error is being reported correctly: https://gitlab.com/gitlab-org/opstrace/tryout-error-tracking/-/error_tracking/4282993888/details but the stacktrace is missing.

The other API calls for capture_error , capture_event and capture_message do not report any http error anymore, but need to confirm if they are ingested correctly. (Note that this are not currently shown in the UI, but should be ingested correctly )

Discussed here: #1737 (comment 1348580935)