fix: accept the ISO-2 country codes when authoring a destination

src/Model/DestinationDto.php

@@ -7,10 +7,26 @@ use Symfony\Component\Validator\Constraints as Assert;
 
 class DestinationDto
 {
+    /**
+     * The countries a destination can be authored in, as German label => ISO-3166-1 alpha-2.
+     *
+     * Both the form's choice list and the constraint below read this one map. They used to
+     * spell the codes out twice and drifted apart the moment the stored values moved to
+     * ISO-2: the form offered 'at' while the constraint still only accepted 'a'.
+     */
+    public const COUNTRIES = [
+        'Österreich' => 'at',
+        'Schweiz' => 'ch',
+        'Frankreich' => 'fr',
+        'Italien' => 'it',
+        'Deutschland' => 'de',
+        'Niederlande' => 'nl',
+    ];
+
     #[Assert\NotBlank(message: 'Bitte angeben')]
     private ?string $product = null;
 
-    #[Assert\Choice(choices: ['a', 'ch', 'd', 'f', 'i', 'nl'], message: 'Ungültige Auswahl')]
+    #[Assert\Choice(callback: 'countryCodes', message: 'Ungültige Auswahl')]
     private ?string $country = null;
 
     #[Assert\NotNull(message: 'Bitte das Beginndatum angeben')]
@@ -46,6 +62,14 @@ class DestinationDto
         return $instance;
     }
 
+    /**
+     * @return list<string>
+     */
+    public static function countryCodes(): array
+    {
+        return array_values(self::COUNTRIES);
+    }
+
     public function getProduct(): ?string
     {
         return $this->product;