[auth-next] feat: $auth.goToLogin -- navigate to login route and redirect on success

[replygirl]

Is your feature request related to a problem? Please describe.

Many auth-guarded components are not directly associated with routes.

Describe the solution you'd like to see

A method call that routes directly to the provided login route--as if the user had tried to access a guarded route--would let us rely exclusively on $auth for simple guards.

Describe alternatives you've considered

As I understand, best practice (and my go-to) is a handler that either:

• navigates to a route named in a from parameter
• checks for a boolean parameter that indicates the handler should call this.$router.back.

[replygirl]

Thanks @hidekatsu-izuno's nuxt-history-state, I've this dirty workaround to rewrite options.redirect.home whenever the user enters my login page:

mounted() {
  const to =
    this.$historyState.getItem?.(Math.max(this.$historyState._page - 1, 0))
      ?.location?.path ?? '/'

  this.$auth.options.redirect.home = to.startsWith('/login') ? '/' : to
},