My problem is:
I have a WordPress website and I want it to work so that every time somebody registers him/herself as a New User on my WordPress site, it triggers a process which takes their login credentials from my WordPress site and uses them to create a new user on a second site, using those same credentials. The second site is a process management tool and is password protected. So this process / script would have to log in to the second site using my login credentials, navigate to the new sub-user registration form and paste in the credentials and submit the form.
I have tried a couple different methods for this already, so far unsuccessful and am unsure what to do next. The second site is called Pruvan. I have checked with them and their API does not support new sub-user registration. I have also tried writing a script that would sit on the Front-End of the WordPress site, gather the new user's login credentials from the DOM, and then make an HTTP Post request to Pruvan's server API. This also did not work. I'm not sure exactly the reason why, but I think it is because Pruvan does not support Cross-Origin Resource Sharing.
I'm trying to find a solution for this problem. Right now I have a vague idea of using a testing framework (such as Selenium) to make a virtual user go to the Pruvan website, log in, and create the sub-user using the login credentials collected from the DOM. The issue I'm having here is that I have no idea how to start making this work with the WordPress Back-End. I have very little experience working with WordPress or PHP and would greatly appreciate some suggestions or a roadmap / blueprint of how you would approach this problem.
Thanks.