Hi, @Erin Kimak Thanks for the question and using the MS Q&A platform
As I understand you want to register App on Azure to use REST API for Azure SQL Database
Permissions needed for the Azure App Registration are going to be very dependent on what the application is going to be trying to do.
As for the resource used to generate the token, I have previously used this resource URI to generate an AD token for PowerShell - I imagine it would also work as such for REST API.
An example that is using PowerShell seems to indicate in the comments that in the App Registration this Resource URI can be found as well (line 21). It also seems to hint at some of the required permissions. I would expect the same to be required between PowerShell and REST API. however, will try to repro this and provide you with more details.
Azure SQL Database Token-based authentication with PowerShell - Microsoft Community Hub
Regards
Geetha