This PowerPlay is about creating a Webhook that is making it possible to create a guest invitation to your tenant with a simple Web Post.
You will get introduce to the concept of creating user names and passwords for Office Graph, technically referred to as client id and client secret – the id being a GUID and the secret a very strong password
The following 2 Microsoft articles cover the topic
- OAuth 2.0 client credentials flow on the Microsoft identity platform | Microsoft Docs
- Create invitation - Microsoft Graph v1.0 | Microsoft Docs
You will find supporting material here