I am currently developing an app that will have synchronization features for Outlook contacts and messages. Then I noticed that both of these have a maximum expiration time of ~3 days.
I need a pointer on how to renew/reauthorize this subscription, I want to use only Delegated permissions because using application permission could be a turndown for our potential user (we don't want to use admin-required permission).
We don't want to rely on the user signing into the app because it's possible that the user doesn't log in to the app for more than three days. However, we need the access token to update the subscription. I considered storing the access token and refresh token of the user encrypted in our database, but I don't like this solution since it adds more complexity and may go against some compliances.
What options do I have?
Also, this documentation authentication section mentions about access token, but it says that it is only used for validation. This section is a bit confusing, can anyone explain?
