fix: Exclude request body in POST and PUT helpers when options are unspecified

[lgarber-akamai]

📝 Description

This change fixes a small issue that made the POST and PUT request helpers encode empty bodies as null, which is rejected by the API. This works by making the options argument variadic and only calling r.SetBody(...) if the argument is specified.

✔️ How to Test

The following test steps assume you have pulled down this PR locally.

Unit Testing

make testunit

Integration Testing

NOTE: This test calls out to the client.ShutdownInstance(...) function, which consumes this helper and does not accept a request body.

make ARGS="-run TestEventPoller_InstancePower" fixtures

Manual Testing

1. In a linodego sandbox environment (e.g. dx-devenv), run the following:

package main

import (
	"context"
	"log"
	"os"

	"github.com/linode/linodego"
)

func main() {
	ctx := context.Background()

	client := linodego.NewClient(nil)
	client.SetToken(os.Getenv("LINODE_TOKEN"))

	inst, err := client.CreateInstance(ctx, linodego.InstanceCreateOptions{
		Region:   "us-mia",
		Type:     "g6-nanode-1",
		Label:    "test-instance",
		Image:    "linode/ubuntu22.04",
		RootPass: "v3rys3cur3t3stp4ssw0rd!!!!",
	})
	if err != nil {
		log.Fatal(err)
	}

	inst, err = client.WaitForInstanceStatus(ctx, inst.ID, linodego.InstanceRunning, 180)
	if err != nil {
		log.Fatal(err)
	}

	// Attempt to shutdown the instance
	// This calls the request helper with no options internally
	if err := client.ShutdownInstance(ctx, inst.ID); err != nil {
		log.Fatal(err)
	}
}

2. Ensure no errors are raised.

[jriddle-linode]

LGTM. passes tests locally

[ykim-akamai]

LGTM