feat(validation): add directive to validate uniqueness of view value
feat(validation): add directive to validate uniqueness of view value

related to CAM-3090

camunda/camunda-bpm-sdk-js,lightswitch05/camunda-bpm-sdk-js,camunda/camunda-bpm-sdk-js,lightswitch05/camunda-bpm-sdk-js,nagyistoce/camunda-bpm-sdk-js,nagyistoce/camunda-bpm-sdk-js