SSA Group has own HR system used by recruiters, people partners, project managers and other staff.
Each user of this system able to create personal events and group events like interviews related to some person. Some time ago company moved to the Office365.
To make easier for the users to manage their activities/book resources was mad decision to integrate HR system with Office 365.
It was done by using Azure AD for authentication of the users and then calling Graph API work with rooms/user calendars in Office365.
Azure AD for authentication
Office 365 integration using Graph API
Microsoft Graph API