Allow us to toggle oauth2 permissions before accepting

When connecting other services to your account, there's a lot of things they can do. Usually, this only includes your username and avatar (for basic identifying info) and sometimes a list of the servers you're in (for example, for a bot dashboard). Some of them, however, force you to include other permissions in order to simply connect. It would be great if we could pick and choose EXACTLY what we want to give something access to before accepting. Of course, this means applications will need to check which permissions were given in order to function properly, and they do have the ability to just flat out deny you if any are missing. However, anything programmed well should be able to let you pass without forcing you to let it join servers for you, for example.