Custom Authentication

Hi node-RED community,

I would like to develop a custom authentication. The authentication will be a Post Http Request with some form-urlencoded parameters in order to identify the user and then to continue the flow to other services (if the user is authorized).

I want to develop a bot. I am using RedBot and I have checked the Authorized Node, but the documentation suggests for custom Authentication calling external links to use the Extend node and to be honest I am confused.

Any suggestions or tips to develop my case? Is there a better way?
Thanks for your time.