We are developing a web application using Microsoft Graph, where the signed in user can, Export all the calendar events to a third party calendar Application. After this initial export, we need to keep the exported data in sync with calendar changes via service app (a scheduled task running on server). This need to be a multi tenant application, as people from different organizations should be able to use this service.
Right now we did the authentication using OAuth 2.0 and OpenID Connect as described in this sample. Later we understood that the access token we get using this method cannot be used in the service app without user interaction. Considering our scenario what is the best way to achieve this?
I have read about App-only authorization method to do this. If we use this authentication method, the app need to be consented by a tenant administrator and the these applications are quite powerful in terms of what data they can access in the Office 365 organization. Considering we are developing a product used by different organizations, will it be feasible to use this method?
