Call external API from MoodleCloud

Hello Community Members,

When I setup a user account within the MoodleCloud, I'd also need to create a user account automatically using the same credentials in an external system. I'm just wondering if this could be achieved via an integration? If so, what integration options do I have within MoodleCloud?

This is what I have learnt so far: 

1. The external system has REST APIs to create user accounts within their system. However, I could not figure out a way to call this API from the MoodleCloud. 
2. I learn that MoodleCloud supports plugin, but not sure if a plugin could be hooked into "create new user" action.

Appreciate any thoughts on the above. Thank you.