feat: implement payment step

src/Form/Model/BankAccountDto.php

@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Form\Model;
+
+use Symfony\Component\Validator\Constraints as Assert;
+
+/**
+ * DTO for bank account information used in payment processing.
+ */
+class BankAccountDto
+{
+    #[Assert\NotBlank(message: 'Bitte geben Sie Ihre IBAN ein.')]
+    #[Assert\Iban(message: 'Die eingegebene IBAN ist ungültig.')]
+    public ?string $iban = null;
+
+    #[Assert\NotBlank(message: 'Bitte geben Sie den Kontoinhaber ein.')]
+    #[Assert\Length(
+        min: 2,
+        max: 70,
+        minMessage: 'Der Kontoinhaber muss mindestens {{ limit }} Zeichen lang sein.',
+        maxMessage: 'Der Kontoinhaber darf maximal {{ limit }} Zeichen lang sein.'
+    )]
+    public ?string $accountHolder = null;
+
+    #[Assert\Length(
+        max: 70,
+        maxMessage: 'Der Bankname darf maximal {{ limit }} Zeichen lang sein.'
+    )]
+    public ?string $bankName = null;
+
+    #[Assert\IsTrue(message: 'Bitte akzeptieren Sie das SEPA-Mandat.')]
+    public bool $sepaMandateAccepted = false;
+
+    /**
+     * Returns IBAN formatted with spaces for display (e.g., DE12 3456 7890 1234 5678 90).
+     */
+    public function getFormattedIban(): ?string
+    {
+        if (null === $this->iban) {
+            return null;
+        }
+
+        $cleanIban = $this->getIbanWithoutSpaces();
+
+        return chunk_split($cleanIban, 4, ' ');
+    }
+
+    /**
+     * Returns IBAN without spaces for storage and API submission.
+     */
+    public function getIbanWithoutSpaces(): ?string
+    {
+        if (null === $this->iban) {
+            return null;
+        }
+
+        return (string) preg_replace('/\s+/', '', $this->iban);
+    }
+}