When attempting to use the OTP method alone, SITE_URL is required (unless you provide a redirect url).
This line in particular leads to a thrown error: https://github.com/get-convex/convex-auth/blob/90318a4d346523035ed9c75e70cd99653a5bede9/src/server/implementation.ts#L1744
I'm not yet processing links inbound to my react native app, so I don't want to use magic links and don't have a redirect url or site url to use, hence my interest in OTP-only.