verify method
Sends a verification email to the specified send-as alias address.
The verification status must be pending. This method is only available
to service account clients that have been delegated domain-wide authority.
Request parameters:
userId - User's email address. The special value "me" can be used to
indicate the authenticated user.
sendAsEmail - The send-as alias to be verified.
$fields - Selector specifying which fields to include in a partial
response.
Completes with a commons.ApiRequestError if the API endpoint returned an error.
If the used http.Client completes with an error when making a REST call,
this method will complete with the same error.
Implementation
async.Future<void> verify(
  core.String userId,
  core.String sendAsEmail, {
  core.String? $fields,
}) async {
  final queryParams_ = <core.String, core.List<core.String>>{
    if ($fields != null) 'fields': [$fields],
  };
  final url_ =
      'gmail/v1/users/' +
      commons.escapeVariable('$userId') +
      '/settings/sendAs/' +
      commons.escapeVariable('$sendAsEmail') +
      '/verify';
  await _requester.request(
    url_,
    'POST',
    queryParams: queryParams_,
    downloadOptions: null,
  );
}