* Fix bug of test stop running when sending a an update to a non existing connection.
* Fix but when querry string support was not equally handled as in AWS.

POST to /@connections/{connectionId} to send message to client at connectionId.

Here's the new way:
  const endpoint=event.requestContext.domainName+'/'+event.requestContext.stage;
  const apiVersion='2018-11-29';
  let API=null;
  if (!process.env.IS_OFFLINE) {
    API = require('aws-sdk');
    require('aws-sdk/clients/apigatewaymanagementapi');
  } else {
    API = require('serverless-offline').AWS;
  }
  return new API.ApiGatewayManagementApi({ apiVersion, endpoint });

1. Action of routes.
2. Listening on WS message sending via REST API.

Doesn't seem to be needed anymore as a workaround in aws-sdk.

Use plain vanilla AWS SDK:
let endpoint=event.apiGatewayUrl;
if (!endpoint) endpoint = event.requestContext.domainName+'/'+event.requestContext.stage;
const apiVersion='2018-11-29';
return new AWS.ApiGatewayManagementApi({ apiVersion, endpoint });

… into websocket-support

In the form of $request.body.x.y.z

… into websocket-support