Support W3C Trace Context and the traceparent header

[wadearnold]

The http client should be able to support the W3C trace context and traceparent header. The library should receive and updated trace from the Moov services. Users of the SDK that are already using open telemetry in their application should have the go/sdk append their traces to ctx

# {version}-{trace_id}-{span_id}-{trace_flags}
traceparent: 00-80e1afed08e019fc1110464cfa66635c-7a085853722dc6d2-01

    client := http.Client{
        // Wrap the Transport with one that starts a span and injects the span context
        // into the outbound request headers.
        Transport: otelhttp.NewTransport(http.DefaultTransport),
        Timeout:   10 * time.Second,
    }

We should write an advanced readme for how to use distributed tracing in the moov-go sdk

[adamdecaf]

Is the W3 trace spec compatible with Open Tracing? I didn't think the two worked together.

[wadearnold]

It is supported by open telemetry
https://github.com/open-telemetry/opentelemetry-go