OpenTelemetry Support

[markdingram]

Problem to solve

Looking to see if Hurl could replace some "handwritten" http tests in Code. Hurl looks like a great fit.

The one missing feature that would make it a direct / drop in replacement would be sending OTEL HTTP Client Traces.

While I have no immediate plans to work on this, I thought to raise an issue from my evaluation.

Proposal

Optionally (through providing a CLI option / Env Var to identify the OTEL collector) produce HTTP Client Traces

Additional context and resources

While the Rust OpenTelemetry crates are commonly used with Tokio there are features to opt-out. Curl should be used as the backing implementation behind the HttpClient.

Tasks to complete

• add https://github.com/open-telemetry/opentelemetry-rust dependency behind a feature flag, implement HttpClient trait with a Curl backed impl
• add CLI option for a OTEL HTTP Trace endpoint
• introduce hooks into request flow that can start / end traces. Follow OTEL Semantic Conventions for HTTP Client Spans.
• periodically dispatch traces / flush at end of test run