Make Retrys by Default for NewFromToken()

[danaelhe]

Configures a retryable client with default behavior when a godo client is initialized via NewFromToken(). Also refactored the code a bit to eliminate code duplication.

If you'd like to test:

func main() {
    ctx := context.Background()
    token := "do_token_here"

    client := godo.NewFromToken(token)

    for i := 0; i < 290; i++ {
        println(i)
        _, resp, _ := client.Account.Get(ctx)
        println(resp.StatusCode)
    }
}

will yield:

2023/08/23 23:43:59 [DEBUG] GET https://api.digitalocean.com/v2/account
117
2023/08/23 23:43:59 [DEBUG] GET https://api.digitalocean.com/v2/account
2023/08/23 23:43:59 [DEBUG] GET https://api.digitalocean.com/v2/account (status: 429): retrying in 7s (4 left)

Same behavior is seen for initializing a client via godo.NewClient()

[andrewsomething]

LGTM! 👍