How to easily get an authentication token to your Office 365 Tenant

I have been developing a backend service that requires a Microsoft Graph token passed up from the frontend. During this development, I have been using Postman to do the call, and have used a simple SPA with authentication to give me a token to my development tenant.

This has been a pretty annoying way to do things when the token expires every half an hour or so, meaning I need to generate another.More