This idea may seem crazy, but is it really possible? I have found Excel API which can be used to edit an excel file located at onedrive, given that, I first sign in to my microsoft account. But I have also found this doc: https://docs.microsoft.com/en-us/graph/auth-v2-service which describes how to get access token without a user and it says:
which is I think, my situation here.
Some apps call Microsoft Graph with their own identity and not on behalf of a user.
So I thought that it's possible. But after hours of trying, I couldn't achieve it. Is it really possible?