feat: use normalized checkbox values in field handlers

tests/Form/Service/ParticipantParkingFieldHandlerTest.php

@@ -37,6 +37,22 @@ class ParticipantParkingFieldHandlerTest extends TestCase
         $this->assertTrue($this->handler->shouldProcess(['some' => 'data'], BookingDto::MODE_EDIT, 5));
     }
 
+    /**
+     * @dataProvider normalizeCheckboxValueCheckedProvider
+     */
+    public function testNormalizeCheckboxValueReturnsTrueWhenChecked(mixed $value): void
+    {
+        $this->assertTrue($this->invokeNormalizeCheckboxValue($value));
+    }
+
+    /**
+     * @dataProvider normalizeCheckboxValueUncheckedProvider
+     */
+    public function testNormalizeCheckboxValueReturnsFalseWhenUnchecked(mixed $value): void
+    {
+        $this->assertFalse($this->invokeNormalizeCheckboxValue($value));
+    }
+
     public function testProcessFieldWithoutParticipant(): void
     {
         $travel = new Travel();
@@ -241,6 +257,40 @@ class ParticipantParkingFieldHandlerTest extends TestCase
         $this->assertNull($participant->parkingService);
     }
 
+    /**
+     * @return array<string, array{mixed}>
+     */
+    public static function normalizeCheckboxValueCheckedProvider(): array
+    {
+        return [
+            'true' => [true],
+            'int 1' => [1],
+            'string 1' => ['1'],
+        ];
+    }
+
+    /**
+     * @return array<string, array{mixed}>
+     */
+    public static function normalizeCheckboxValueUncheckedProvider(): array
+    {
+        return [
+            'false' => [false],
+            'int 0' => [0],
+            'string 0' => ['0'],
+            'empty string' => [''],
+            'null' => [null],
+            'non-numeric string' => ['off'],
+        ];
+    }
+
+    private function invokeNormalizeCheckboxValue(mixed $value): bool
+    {
+        $reflection = new \ReflectionMethod($this->handler, 'normalizeCheckboxValue');
+
+        return $reflection->invoke($this->handler, $value);
+    }
+
     private function createTransportationService(string $subType): Service
     {
         $service = new Service();