HTTPS health monitor with username and credential check

on F5 12.1.1

 

I would like to check the functionality of a login page and noticed the health monitors have a username/password field. If I have a user account for the webpage how do I word the send/receive string? I'm assuming I have to use POST but I don't know what format I need to put it in.

 

I found an article saying the username:password needs to be changed to base64. I just want some guidance on how to format a monitor that logs into a URL. Looking this up I found that you can test logging into a webpage from the shell using:

 

openssl s_client -host -port <443>

 

but I don't know what POST I should do after that.