Merge interesting parts of behat/rest-extension

[stof]

@jakzal started https://github.com/jakzal/RestExtension for a similar purpose. The interesting parts of the extension should be merged here.

I'm thinking in particular to the response matcher, which is something I wanted to implement in WebApiExtension. The library used in the RestExtension seems to fit very well with what I have in mind.

[fesor]

I think it will be better if this will be a separate packages. This gives more flexibility for developer, who will decide which library he wants to use to make requests (webapiextension or just custom steps with curl/guzzle) and check responses. You can use ApiClientAwareContext and provide to user similar interface to inject response. For example my json_spec provides JsonProviderInterface for this purposes.

[tyx]

Since yesterday JsonContext from behatch-context is totally decoupled from its RestContext :
https://github.com/sanpii/behatch-contexts/blob/master/src/Context/JsonContext.php

So it become very simple to use it with WebApiContext. Here is a Poc I currently use :
tyx@58d832a

[fesor]

@tyx, i guess simple wrapping and replacing GuzzleHttp\Client in container may do the trick. I prepared PR #16 to this purposes. I think it is a best solution as it doesn't involve library user at all, just add extension and context and you ready to go.

[yosmanyga]

This extension uses PHPUnit_Framework_Assert. I can't see how to use coduo/php-matcher? Do you have any plan?