How to implement users' consent for Microsoft Graph and reservation room

Question

Dear all,

we need to implement a possibility to our users (in our application) to book some reservations in a room (like a meeting in a room with several users).
Our need is to allow the application to list all available rooms, create/modify/delete room's booking.
We saw that 2 type of existing authentifications, "application" and "delegate" ... we are really out of focus to understand this concept.
We would like to have the opportunity to ask to the current logged user the permission to access to his calendar like a promp to him and let him give or not access to his calendar.
Did you think is a good idea ?

How we can do that, because we search in the Microsoft API Graph how to modify user consent to share his calendar.

What do you think ? Is a good approach ? We have somes doubts how to authentificate to API Graph, how to manage this feature for example just one connection with clientid, secretid, tenantid and ask at any time the user consent, or is possible to connect current user with his credential to Graph API ?

Do we need to also share room's calendar to ?

Someone can help us plz ?

thank you very much

Adrien