nrslog: Logs in context does not work with durations

[frankywahl]

Description

Structured logging in go can use the nrslog.Duration type to define an attribute. However, that does not get reported as a duration, but instead gets reported as the string time.Duration

Steps to Reproduce

The following code sample is based from the example in https://github.com/newrelic/go-agent/blob/master/v3/integrations/logcontext-v2/nrslog/example/main.go and adds a slog.Duration attribute when logging.

package main

import (
	"context"
	"log/slog"
	"os"
	"time"

	"github.com/newrelic/go-agent/v3/integrations/logcontext-v2/nrslog"
	"github.com/newrelic/go-agent/v3/newrelic"
)

func main() {
	app, err := newrelic.NewApplication(
		newrelic.ConfigAppName("slog example app"),
		newrelic.ConfigFromEnvironment(),
		newrelic.ConfigAppLogEnabled(true),
	)
	if err != nil {
		panic(err)
	}

	app.WaitForConnection(time.Second * 5)
	log := slog.New(nrslog.TextHandler(app, os.Stdout, &slog.HandlerOptions{}))

	log.Info("I am a log message")

	txn := app.StartTransaction("example transaction")
	ctx := newrelic.NewContext(context.Background(), txn)

	log.InfoContext(ctx, "I am a log inside a transaction with custom attributes!",
		slog.String("foo", "bar"),
		slog.Int("answer", 42),
		slog.Duration("duration", 3*time.Second),
		slog.Any("some_map", map[string]interface{}{"a": 1.0, "b": 2}),
	)

	// pretend to do some work
	time.Sleep(500 * time.Millisecond)
	log.Warn("Uh oh, something important happened!")
	txn.End()

	log.Info("All Done!")

	app.Shutdown(time.Second * 10)
}

Expected Behavior

An actual duration (as integer, or float based on the unit) would be populated instead of the string.

Your Environment

Go: 1.24
Go-Agent: v3.38.0

Reproduction case

Additional context

Note: time.Time has similar issues in that it comes as a string timestamp which NR would then have to parse.