Problem/Motivation
UniqueFieldValueValidator assumes that the host entity is always defined with integer IDs. During the validation, it adds this condition to the entity query:
->condition($id_key, (int) $items->getEntity()->id(), '<>')
Note the entity ID typecasting.
Proposed resolution
Make it work also for content entities with string IDs.
Remaining tasks
None.
User interface changes
None.
API changes
None.
Data model changes
None.
Release notes snippet
N/A
