User configurable locale (language) (#10204)

* Support for system APP_LOCALE

* Start preferences re-write

* port 2fa form

* Working user preferences

* Language user preference

* Don't look up locale from the DB every request

* Device list working

* Deny demo user middleware

* Finish password changing

* remove used resource methods

* remove leftover use

* warn that translation is incomplete

* fix style

app/Http/Middleware/SetLocale.php

@@ -0,0 +1,34 @@
+<?php
+
+namespace App\Http\Middleware;
+
+use App;
+use App\Models\UserPref;
+use Closure;
+use Session;
+
+class SetLocale
+{
+    /**
+     * Handle an incoming request.
+     *
+     * @param  \Illuminate\Http\Request  $request
+     * @param  \Closure  $next
+     * @return mixed
+     */
+    public function handle($request, Closure $next)
+    {
+        if (Session::has('locale')) {
+            $locale = Session::get('locale');
+        } elseif (!is_null($request->user())) {
+            $locale = UserPref::getPref($request->user(), 'locale');
+            Session::put('locale', $locale);
+        }
+
+        if (!empty($locale)) {
+            App::setLocale($locale);
+        }
+
+        return $next($request);
+    }
+}