I am writing a Sharepoint Online add-in in c# that is supposed to collect data from multiple users and store that somewhere where only their version of the app and I can access it. To be more specific - user 1 clicks a button, a text file 1 is created somewhere (if it doesn't already exist) and that's the only file user 1 can access. User 2 does the same, but a distinct file 2 is created. User 2 can't collect data from file 1 and vice versa. Of course it doesn't have to be files. The app has to be able to both read and write data.
I am trying to figure out where to even begin, I was thinking of creating a database in Azure but I'm wondering if there might be easier ways.