requestWantsTrace returns true if a request is opting into tracing either via our HTTP Header or our URL Query.

ShouldTrace returns true if the shouldTraceKey context value is true.

WithShouldTrace sets the shouldTraceKey context value.

TraceAll turns on tracing for all requests.

TraceNone turns off tracing.

TraceSelective turns on tracing only for requests with the X-Sourcegraph-Should-Trace header set to a truthy value.

ShouldTracePropagator implements (internal/grpc).Propagator so that the ShouldTrace key can be propagated across gRPC API calls.

Transport wraps an underlying HTTP RoundTripper, injecting the X-Sourcegraph-Should-Trace header into outgoing requests whenever the shouldTraceKey context value is true.