How to integrate IS with external API ? Ex: VideoCall Service

what do you mean by integrating with IS? Is it just Integrating with application working on IS? Years ago, I've implemented some of the video services into our application. So, I have some experience. But this time it could be even less complex, or completely different. And anyway depends on how exactly you would like to see it. I can help you with it, please contact me directly dmitry@caretdev.com, I co-founder of a company, where we can help you to implement this or anything else.