Update OAuth2 Base authorization URL

[Zoddo]

This remove a useless redirect and allows for a nicer error when an invalid scope is sent (this vs this).

The URL generator on the dev portal can also be updated to remove /api from the path.

[ckohen]

Think maybe there should be a note on why this is different.

Don't know if this should be part of that note, but using the /api route causes all subdomains to redirect to stable discord as well which is a huge pain in the butt when you're only logged in to canary or ptb on web.