feat(validator): Added validation rule for associations

src/validator/has-association.js

@@ -0,0 +1,13 @@
import {ValidationRule} from 'aurelia-validation';
import {Entity} from '../index';

export class HasAssociationValidationRule extends ValidationRule {
  constructor() {
    super(
      null,
      value => !!((value instanceof Entity && typeof value.id === 'number') || typeof value === 'number'),
      null,
      'isRequired'
    );
  }
}