clearer error if endpoint missing DeviceAuthURL

Author: hickford

deviceauth.go

@@ -88,6 +88,10 @@ func (c *Config) DeviceAuth(ctx context.Context, opts ...AuthCodeOption) (*Devic
 }
 
 func retrieveDeviceAuth(ctx context.Context, c *Config, v url.Values) (*DeviceAuthResponse, error) {
+	if c.Endpoint.DeviceAuthURL == "" {
+		return nil, fmt.Errorf("endpoint missing DeviceAuthURL")
+	}
+
 	req, err := http.NewRequest("POST", c.Endpoint.DeviceAuthURL, strings.NewReader(v.Encode()))
 	if err != nil {
 		return nil, err