Worked on MFA setup required flow

- Restructured some of the route naming to be a little more consistent.
- Moved the routes about to be more logically in one place.
- Created a new middleware to handle the auth of people that should be
  allowed access to mfa setup routes, since these could be used by
  existing logged in users or by people needing to setup MFA on access.
- Added testing to cover MFA setup required flow.
- Added TTL and method tracking to session last-login tracking system.

app/Http/Middleware/Authenticate.php

@@ -15,9 +15,8 @@ class Authenticate
         if (!hasAppAccess()) {
             if ($request->ajax()) {
                 return response('Unauthorized.', 401);
-            } else {
-                return redirect()->guest(url('/login'));
             }
+            return redirect()->guest(url('/login'));
         }
 
         return $next($request);

app/Http/Middleware/AuthenticatedOrPendingMfa.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace BookStack\Http\Middleware;
+
+use BookStack\Auth\Access\LoginService;
+use BookStack\Auth\Access\Mfa\MfaSession;
+use Closure;
+
+class AuthenticatedOrPendingMfa
+{
+
+    protected $loginService;
+    protected $mfaSession;
+
+    public function __construct(LoginService $loginService, MfaSession $mfaSession)
+    {
+        $this->loginService = $loginService;
+        $this->mfaSession = $mfaSession;
+    }
+
+
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @return mixed
+     */
+    public function handle($request, Closure $next)
+    {
+        $user = auth()->user();
+        $loggedIn = $user !== null;
+        $lastAttemptUser = $this->loginService->getLastLoginAttemptUser();
+
+        if ($loggedIn || ($lastAttemptUser && $this->mfaSession->isPendingMfaSetup($lastAttemptUser))) {
+            return $next($request);
+        }
+
+        return redirect()->guest(url('/login'));
+    }
+}