My Sagemcom F@st router doesnt have Dynu as a predefined DDNS provider. When I am trying to setup Dynu as a custom DDNS service it asks a field for "Request" . A predefined sample value is provided as below:

http://members.dyndns.org/nic/update?system=custom&hostname=[DOMAIN]&myip=[IP]

How do I interpret this for Dynu?

attaching a screenshot and your help is highly appreciated

Server: api.dynu.com
Request: https://api.dynu.com/nic/update?hostname=[DOMAIN]&myip=[IP]