Add login via Facebook; login dialog

[koistya]

• api: Add Facebook OAuth 2.0 authentication middleware (api/auth/facebook.ts)
• api: Improve req.signIn() function to be used with the updated OAuth 2.0 authentication flow
• api: Update OAuth 2.0 response HTML to be compatible with the modal login window (api/auth/response.hbs)
• web: Add LoginDialog that shows Google / Facebook login options
• web: Remove useAuth() React hook in favor of useLoginDialog(), useSignOut()
• web: Small improvement to useErrors React hook

How to open a login (modal) dialog?

import * as React from "react";
import { useLoginDialog } from "../hooks";

export function Example(): JSX.Element {
  const loginDialog = useLoginDialog();

  return (
    <div>
      <button onClick={loginDialog.show}>Log In</button>
    </div>
  );
}

No Redux required! 👍🏻