create method
Create a new channel in a particular project and location.
request - The metadata request object.
Request parameters:
parent - Required. The parent collection in which to add this channel.
Value must have pattern ^projects/\[^/\]+/locations/\[^/\]+$.
channelId - Required. The user-provided ID to be assigned to the
channel.
validateOnly - Optional. If set, validate the request and preview the
review, but do not post it.
$fields - Selector specifying which fields to include in a partial
response.
Completes with a GoogleLongrunningOperation.
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<GoogleLongrunningOperation> create(
  Channel request,
  core.String parent, {
  core.String? channelId,
  core.bool? validateOnly,
  core.String? $fields,
}) async {
  final body_ = convert.json.encode(request);
  final queryParams_ = <core.String, core.List<core.String>>{
    if (channelId != null) 'channelId': [channelId],
    if (validateOnly != null) 'validateOnly': ['${validateOnly}'],
    if ($fields != null) 'fields': [$fields],
  };
  final url_ = 'v1/' + core.Uri.encodeFull('$parent') + '/channels';
  final response_ = await _requester.request(
    url_,
    'POST',
    body: body_,
    queryParams: queryParams_,
  );
  return GoogleLongrunningOperation.fromJson(
      response_ as core.Map<core.String, core.dynamic>);
}