setValidationErrors(errors) {
    const previousValidationErrors = this._validationErrors.map((o) => o.name);
    const newValidationErrors = errors.map((o) => o.name);

    this._validationErrors = errors;

    // Mark all previous plus all new as changed
    const changedKeys = previousValidationErrors.concat(newValidationErrors);
    this._markKeysChanged(changedKeys);
  }
Merges existing with a list of new validation errors.
Reactive.
@param errors ValidationError[]