fix: Prevent unexpected warning from Resty when calling Client.SetDebug(false)

[lgarber-akamai]

📝 Description

This pull request fixes a small issue that would cause the following Resty warning (raised here) to be printed when Client.SetDebug(...) is called multiple times:

WARN RESTY Overwriting an existing on-request-log callback from=github.com/linode/linodego.(*Client).SetDebug.(*Client).sanitizeAuthorizationHeader.func1 to=github.com/linode/linodego.(*Client).SetDebug.(*Client).sanitizeAuthorizationHeader.func1

This works by initializing the log hook during client creation rather than when calling SetDebug(...).

✔️ How to Test

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

Manual Testing

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

package main

import (
	"github.com/linode/linodego"
)

func main() {
	client := linodego.NewClient(nil)
	client.SetDebug(true)
	client.SetDebug(true)
	client.SetDebug(false)
}

2. Ensure no warnings are raised from Resty.

[yec-akamai]

No warnings from Resty anymore, nice work!

[jriddle-linode]

LGTM

[ykim-akamai]

LGTM, nice work!