Fix TracingUUID toString string format

[changm4n]

What and why?

There is a bug in the creation of the traceparent of the trace http header.
The type of TracingUUID.rawValue is UInt64, but it is converted to 32 bits when converted like [format: "%16x"].
When trace id : 7242571286695202638(decimal), the traceparent header value is being generated as [version]-00000000000000000000000063e94f4e-[parent id]-[trace flags] now.

How?

Use the %llx format when converting strings of type UInt64.

Review checklist

• Feature or bugfix MUST have appropriate tests (unit, integration)
• Make sure each commit and the PR mention the Issue number or JIRA reference
• Add CHANGELOG entry for user facing changes

Custom CI job configuration (optional)

• Run unit tests
• Run integration tests
• Run smoke tests

[maciejburda]

Thank you for the contribution! That's a great catch!

[maciejburda]

[ncreated]

Thanks a million @changm4n 🏅. We haven't heard of this causing a problem before, could you please describe what was the impact on your side?

[changm4n]

@ncreated The datadog agent on the backend was using the trace id in the request header received from the client, but the trace id sent to datadog from the client was different from the trace id sent to datadog from the backend, so it was being recognised as a different trace.

[ncreated]

@ncreated The datadog agent on the backend was using the trace id in the request header received from the client, but the trace id sent to datadog from the client was different from the trace id sent to datadog from the backend, so it was being recognised as a different trace.

Thank you @changm4n, that helps us prioritising release of this fix 👍