v4.1.0
feat: methods added to unique collection: mapWithCustomKey, findFirstByCondition, isNotEmpty, jsonSerialize,
refactor: removed abstract from unique collection (it is not necessary to extend this class)
feat: methods added to unique collection: mapWithCustomKey, findFirstByCondition, isNotEmpty, jsonSerialize,
refactor: removed abstract from unique collection (it is not necessary to extend this class)