fix: propagate OTel trace context through the func runtime

[Nachiket-Roy]

Changes

This PR resolves issue knative/func#3866 where OpenTelemetry trace propagation would break between Knative's queue proxy and deployed Go functions.

OTel Trace Context Propagation:

• Configured a global TextMapPropagator using a composite W3C Trace Context and Baggage propagator in both HTTP and CloudEvents services.
• Wrapped the HTTP receiver handlers with otelhttp.NewHandler to extract incoming traceparent/tracestate headers and inject the extracted context into the request context before passing it to the function's handler.

/kind bug

Fixes knative/func#3866

Fixes an issue where OpenTelemetry trace context was dropped between Knative's queue proxy and Go functions. The runtime now correctly extracts W3C trace context headers and propagates them to the context passed to function handlers.

[knative-prow]

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[knative-prow]

Welcome @Nachiket-Roy! It looks like this is your first PR to knative-extensions/func-go 🎉

[Copilot]

Pull request overview

This PR fixes OpenTelemetry trace context propagation for Go functions running behind Knative’s queue-proxy by ensuring W3C traceparent/tracestate headers are extracted on ingress and made available via context.Context to function handlers.

Changes:

• Configure a W3C Trace Context + Baggage TextMapPropagator and wrap HTTP/CloudEvents receivers with otelhttp.NewHandler.
• Add tests validating that an incoming traceparent results in a valid span context in the handler.
• Add OpenTelemetry dependencies to go.mod/go.sum.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
http/service.go	Adds global propagator configuration and wraps the root handler with otelhttp for context extraction.
http/service_test.go	Adds coverage for trace-context propagation into HTTP handler contexts.
cloudevents/service.go	Adds global propagator configuration and wraps the CloudEvents receiver with otelhttp.
cloudevents/service_test.go	Adds coverage for trace-context propagation into CloudEvents handler contexts.
go.mod	Introduces OpenTelemetry module requirements used by the runtime/tests.
go.sum	Updates sums for newly introduced OpenTelemetry and transitive dependencies.

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[knative-prow-robot]

PR needs rebase.

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