Support unique values within the bundle

Problem/Motivation

In some case we want to limit unique value within the bundle of the specific entity type. Example like this https://www.drupal.org/docs/drupal-apis/entity-api/entity-validation-api... or the one in the description of #2973455: Unique field constraint does not work with any field main property name that is not "value" make it feel like it is possible, but UniqueField constraint doesn't support it.

One could even argue that this is a bug, but that is not so important.

Steps to reproduce

• Add the UniqueField constraint to a specific bundle field with something like:
  

  /**
     * Prevent duplicated in my_bundle.
     */
    #[Hook('entity_bundle_field_info_alter')]
    public function uniqueBundleField(&$fields, EntityTypeInterface $entity_type, $bundle) {
  
      $field_name = 'field_name';
      if (isset($fields[$field_name])) {
        $fields[$field_name]->addConstraint('UniqueField', []);
      }
      if ($entity_type->id() === 'entity_type' && $bundle === 'my_bundle') {
        if (isset($fields[$field_name])) {
          $fields[$field_name]->addConstraint('UniqueField', []);
        }
      }
    }
  

• create an entity of "entity_type" and bundle other than "my_bundle" with the "field_name" value of "field_value"
• create an entity of "entity_type" and bundle "my_bundle" with the "field_name" value of "field_value"
• observe the duplicated error message

Proposed resolution

Add support for limiting duplicates check within a configured bundle

Remaining tasks

implement
review
commit

API changes

Addition of the bundle configuration option to the UniqueFieldConstraint

Release notes snippet

TBD