Added API endpoints to fetch invoices (#5070)

* added serializer attributes for API usage
* new setters to fill invoice data from fixture
* re-usable fixture helper methods
* added API endpoints to fetch invoices
* adjust tests

tests/DataFixtures/FixturesTrait.php

@@ -0,0 +1,91 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Tests\DataFixtures;
+
+use App\Entity\Activity;
+use App\Entity\Customer;
+use App\Entity\Project;
+use App\Entity\User;
+use Doctrine\Persistence\ObjectManager;
+
+trait FixturesTrait
+{
+    /**
+     * @return array<int, User>
+     */
+    private function getAllUsers(ObjectManager $manager): array
+    {
+        $all = [];
+        /** @var User[] $entries */
+        $entries = $manager->getRepository(User::class)->findAll();
+        foreach ($entries as $temp) {
+            if ($temp->getId() === null) {
+                continue;
+            }
+            $all[$temp->getId()] = $temp;
+        }
+
+        return $all;
+    }
+
+    /**
+     * @return array<int, Customer>
+     */
+    private function getAllCustomers(ObjectManager $manager): array
+    {
+        $all = [];
+        /** @var Customer[] $entries */
+        $entries = $manager->getRepository(Customer::class)->findAll();
+        foreach ($entries as $temp) {
+            if ($temp->getId() === null) {
+                continue;
+            }
+            $all[$temp->getId()] = $temp;
+        }
+
+        return $all;
+    }
+
+    /**
+     * @return array<int, Project>
+     */
+    private function getAllProjects(ObjectManager $manager): array
+    {
+        $all = [];
+        /** @var Project[] $entries */
+        $entries = $manager->getRepository(Project::class)->findAll();
+        foreach ($entries as $temp) {
+            if ($temp->getId() === null) {
+                continue;
+            }
+            $all[$temp->getId()] = $temp;
+        }
+
+        return $all;
+    }
+
+    /**
+     * @return array<int, Activity>
+     */
+    private function getAllActivities(ObjectManager $manager): array
+    {
+        $all = [];
+        /** @var Activity[] $entries */
+        $entries = $manager->getRepository(Activity::class)->findAll();
+        foreach ($entries as $temp) {
+            if ($temp->getId() === null) {
+                continue;
+            }
+            $all[$temp->getId()] = $temp;
+        }
+
+        return $all;
+    }
+}