Release 8.0.0-RC1

This the first release candidate for 8.0.0 it contains some new features and changes with the previous 7.x Elastic PHP client.

Changes

• the ConnectionPool namespace has been renamed in NodePool, consequently all the Connection classes has been renamed in Node
• the previous Apache 2.0 LICENSE has been changed in MIT

New features

• added the usage of HTTPlug library to autodiscovery PSR-18 client and HttpAsyncClient interface using Promise.
• added the Trasnport::sendAsyncRequest(RequestInterface $request): Promise to send a PSR-7 request using asynchronous request
• added the Transport::setAsyncClient(HttpAsyncClient $asyncClient) and Transport::getAsyncClient() functions. If the PSR-18 client already implements the HttpAsyncClient interface you don't need to use the setAsyncClient() function, it will discovered automatically
• added the Transport::setRetries() function to specify the number of HTTP request retries to apply. If the HTTP failures exceed the number of retries the client generates a NoNodeAvailableException