Changed logic to list domains to centralize conditions in service

module/Core/src/Domain/Model/DomainItem.php

@@ -0,0 +1,37 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Core\Domain\Model;
+
+use JsonSerializable;
+
+final class DomainItem implements JsonSerializable
+{
+    private string $domain;
+    private bool $isDefault;
+
+    public function __construct(string $domain, bool $isDefault)
+    {
+        $this->domain = $domain;
+        $this->isDefault = $isDefault;
+    }
+
+    public function jsonSerialize(): array
+    {
+        return [
+            'domain' => $this->domain,
+            'isDefault' => $this->isDefault,
+        ];
+    }
+
+    public function toString(): string
+    {
+        return $this->domain;
+    }
+
+    public function isDefault(): bool
+    {
+        return $this->isDefault;
+    }
+}