Move to Symfony Flex

The structure changed completely.
Bundles are gone. Everything is flatten in the folder `src`.
I separated import & api controllers to avoid _pollution_ in the main controller folder.

tests/Form/DataTransformer/StringToListTransformerTest.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace App\Tests\Form\DataTransformer;
+
+use App\Form\DataTransformer\StringToListTransformer;
+use PHPUnit\Framework\TestCase;
+
+class StringToListTransformerTest extends TestCase
+{
+    /**
+     * @dataProvider transformProvider
+     */
+    public function testTransformWithValidData($inputData, $expectedResult)
+    {
+        $transformer = new StringToListTransformer();
+
+        $this->assertSame($expectedResult, $transformer->transform($inputData));
+    }
+
+    public function transformProvider()
+    {
+        return [
+            [null, ''],
+            [[], ''],
+            [['single value'], 'single value'],
+            [['first value', 'second value'], 'first value,second value'],
+        ];
+    }
+
+    /**
+     * @dataProvider reverseTransformProvider
+     */
+    public function testReverseTransformWithValidData($inputData, $expectedResult)
+    {
+        $transformer = new StringToListTransformer();
+
+        $this->assertSame($expectedResult, $transformer->reverseTransform($inputData));
+    }
+
+    public function reverseTransformProvider()
+    {
+        return [
+            [null, null],
+            ['', []],
+            ['single value', ['single value']],
+            ['first value,second value', ['first value', 'second value']],
+            ['first value,     second value', ['first value', 'second value']],
+            ['first value,  ,  second value', ['first value', 'second value']],
+        ];
+    }
+}