Add client.OnBeforeRequest(...) (#250)

client.go

@@ -114,6 +114,8 @@ type Client struct {
 	Volumes                  *Resource
 }
 
+type Request = resty.Request
+
 func init() {
 	// Wether or not we will enable Resty debugging output
 	if apiDebug, ok := os.LookupEnv("LINODE_DEBUG"); ok {
@@ -151,6 +153,13 @@ func (c *Client) SetDebug(debug bool) *Client {
 	return c
 }
 
+// OnBeforeRequest adds a handler to the request body to run before the request is sent
+func (c *Client) OnBeforeRequest(m func(request *Request) error) {
+	c.resty.OnBeforeRequest(func(client *resty.Client, req *resty.Request) error {
+		return m(req)
+	})
+}
+
 // SetBaseURL sets the base URL of the Linode v4 API (https://api.linode.com/v4)
 func (c *Client) SetBaseURL(baseURL string) *Client {
 	baseURLPath, _ := url.Parse(baseURL)