Bug #5161 Disallow clear in AssociationField when field is required

Closes #5161

Author: Sobak

src/Field/AssociationField.php

@@ -11,7 +11,9 @@
  */
 final class AssociationField implements FieldInterface
 {
-    use FieldTrait;
+    use FieldTrait {
+        FieldTrait::setRequired as parentSetRequired;
+    }
 
     public const OPTION_AUTOCOMPLETE = 'autocomplete';
     public const OPTION_EMBEDDED_CRUD_FORM_CONTROLLER = 'crudControllerFqcn';
@@ -91,6 +93,14 @@ public function setQueryBuilder(\Closure $queryBuilderCallable): self
         return $this;
     }
 
+    public function setRequired(bool $isRequired): self
+    {
+        $this->parentSetRequired($isRequired);
+        $this->setHtmlAttribute('required', $isRequired);
+
+        return $this;
+    }
+
     public function renderAsEmbeddedForm(?string $crudControllerFqcn = null, ?string $crudNewPageName = null, ?string $crudEditPageName = null): self
     {
         $this->setCustomOption(self::OPTION_RENDER_AS_EMBEDDED_FORM, true);