Add API (#606)

This is the first part of the API. It supports most of contacts, as well as the
journal. This PR also brings Monica to Laravel 5.5, as the API required it with
the new concept of resources. It needs to run `php artisan migrate` as well as
`php artisan passport:keys` to generate the access tokens needed for the API.

app/Http/Controllers/Api/ApiController.php

@@ -0,0 +1,185 @@
+<?php
+
+namespace App\Http\Controllers\Api;
+
+use App\ApiUsage;
+use Illuminate\Http\Request;
+use App\Http\Controllers\Controller;
+
+class ApiController extends Controller
+{
+    /**
+     * @var int
+     */
+    protected $httpStatusCode = 200;
+
+    /**
+     * @var int
+     */
+    protected $errorCode;
+
+    /**
+     * @var int
+     */
+    protected $limitPerPage = 10;
+
+    public function __construct()
+    {
+        $this->middleware(function ($request, $next) {
+            $apiUsage = (new ApiUsage)->log($request);
+
+            if ($request->has('limit')) {
+                if ($request->get('limit') > config('api.max_limit_per_page')) {
+                    return $this->setHTTPStatusCode(400)
+                              ->setErrorCode(30)
+                              ->respondWithError(config('api.error_codes.30'));
+                }
+
+                $this->setLimitPerPage($request->get('limit'));
+            }
+
+            // make sure the JSON is well formatted if the given call sends a JSON
+            // TODO: there is probably a much better way to do that
+            if ($request->method() != 'GET' and $request->method() != 'DEL') {
+                if (is_null(json_decode($request->getContent()))) {
+                    return $this->setHTTPStatusCode(400)
+                              ->setErrorCode(37)
+                              ->respondWithError(config('api.error_codes.37'));
+                }
+            }
+
+            return $next($request);
+        });
+    }
+
+    /**
+     * Default request to the API.
+     * @return json
+     */
+    public function success()
+    {
+        return $this->respond([
+            'success' => [
+                'message' => 'Welcome to Monica',
+            ],
+        ]);
+    }
+
+    /**
+     * @return int
+     */
+    public function getHTTPStatusCode()
+    {
+        return $this->httpStatusCode;
+    }
+
+    /**
+     * @param int $statusCode
+     * @return $this
+     */
+    public function setHTTPStatusCode($statusCode)
+    {
+        $this->httpStatusCode = $statusCode;
+
+        return $this;
+    }
+
+    /**
+     * @return int
+     */
+    public function getErrorCode()
+    {
+        return $this->errorCode;
+    }
+
+    /**
+     * @param int $errorCode
+     * @return $this
+     */
+    public function setErrorCode($errorCode)
+    {
+        $this->errorCode = $errorCode;
+
+        return $this;
+    }
+
+    /**
+     * @return int
+     */
+    public function getLimitPerPage()
+    {
+        return $this->limitPerPage;
+    }
+
+    /**
+     * @param int $limit
+     * @return $this
+     */
+    public function setLimitPerPage($limit)
+    {
+        $this->limitPerPage = $limit;
+
+        return $this;
+    }
+
+    /**
+     * Sends a JSON to the consumer.
+     * @param  array $data
+     * @param  array  $headers [description]
+     * @return Response
+     */
+    public function respond($data, $headers = [])
+    {
+        return response()->json($data, $this->getHTTPStatusCode(), $headers);
+    }
+
+    /**
+     * Sends a response not found (404) to the request.
+     * @param string $message
+     */
+    public function respondNotFound($message = 'Not found!')
+    {
+        return $this->setHTTPStatusCode(404)
+                    ->setErrorCode(31)
+                    ->respondWithError($message);
+    }
+
+    /**
+     * Sends an error when the query didn't have the right parameters for
+     * creating an object.
+     * @param string $message
+     */
+    public function respondNotTheRightParameters($message = 'Too many parameters')
+    {
+        return $this->setHTTPStatusCode(500)
+                    ->setErrorCode(33)
+                    ->respondWithError($message);
+    }
+
+    /**
+     * Sends a response with error.
+     * @param string message
+     */
+    public function respondWithError($message)
+    {
+        return $this->respond([
+            'error' => [
+                'message' => $message,
+                'error_code' => $this->getErrorCode(),
+            ],
+        ]);
+    }
+
+    /**
+     * Sends a response that the object has been deleted, and also indicates
+     * the id of the object that has been deleted.
+     * @param  int $id
+     */
+    public function respondObjectDeleted($id)
+    {
+        return $this->respond([
+            'deleted' => true,
+            'id' => $id,
+        ]);
+    }
+}