Added status endpoint

For #2467

app/Http/Controllers/StatusController.php

@@ -0,0 +1,47 @@
+<?php namespace BookStack\Http\Controllers;
+
+use Illuminate\Support\Facades\Cache;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Session;
+use Illuminate\Support\Str;
+
+class StatusController extends Controller
+{
+
+    /**
+     * Show the system status as a simple json page.
+     */
+    public function show()
+    {
+        $statuses = [
+            'database' => $this->trueWithoutError(function () {
+                return DB::table('migrations')->count() > 0;
+            }),
+            'cache' => $this->trueWithoutError(function () {
+                $rand = Str::random();
+                Cache::set('status_test', $rand);
+                return Cache::get('status_test') === $rand;
+            }),
+            'session' => $this->trueWithoutError(function () {
+                $rand = Str::random();
+                Session::put('status_test', $rand);
+                return Session::get('status_test') === $rand;
+            }),
+        ];
+
+        $hasError = in_array(false, $statuses);
+        return response()->json($statuses, $hasError ? 500 : 200);
+    }
+
+    /**
+     * Check the callable passed returns true and does not throw an exception.
+     */
+    protected function trueWithoutError(callable $test): bool
+    {
+        try {
+            return $test() === true;
+        } catch (\Exception $e) {
+            return false;
+        }
+    }
+}