how about removing default value for NEXTAUTH_URL?

[bmyun]

Description 📓

I was developing it with https (https://localhost:3443), I forgot setting NEXTAUTH_URL.
However, the error did not occur because of the code below.
Even though it wasn't intended, This code makes all redirection and callbacks redirect to http://localhost:3000
I think it must occur an error and developer must realize the mistakes in the build or test time.
And default value is localhost, so it shouldn't offer any help on live.
It makes my project run well only locally!

export default function parseUrl(url?: string): InternalUrl {
  const defaultUrl = new URL("http://localhost:3000/api/auth")

  if (url && !url.startsWith("http")) {
    url = `https://${url}`
  }

  const _url = new URL(url ?? defaultUrl)
  const path = (_url.pathname === "/" ? defaultUrl.pathname : _url.pathname)
    // Remove trailing slash
    .replace(/\/$/, "")

  const base = `${_url.origin}${path}`

  return {
    origin: _url.origin,
    host: _url.host,
    path,
    base,
    toString: () => base,
  }
}

How to reproduce ☕️

export default function parseUrl(url: string): InternalUrl {
  const _url = new URL(url) // when url is undefined, it should be cause an error
  const path = (_url.pathname === "/" ? '/api/auth' : _url.pathname)
    // Remove trailing slash
    .replace(/\/$/, "")

  const base = `${_url.origin}${path}`

  return {
    origin: _url.origin,
    host: _url.host,
    path,
    base,
    toString: () => base,
  }
}

Contributing 🙌🏽

Yes, I am willing to help implement this feature in a PR