Support API Platform and multiple response content types

[warmwaterkruik]

Support API Platform and multiple response content types: application/ld+json application/hal+json application/vnd.api+json content types through optional accept headers.

• The previous apip-demo.json schema contained old invalid references. Fixed with latest demo.json schema
• The client endpoint methods will now accept an optional array $accept parameter if there are multiple content types available as a response. API Platform can return ld+json or hal+json responses based on the Accept header.
• The endpoint response body transfer will now transform LdJson and HalJson json responses into concrete objects based on the response content type.

[Korbeil]

It looks really good !
I will make a test on a code-base I have at work to make sure everything is fine since there is a lot of impactful changes. And I'll merge that if it's good.

Could you add a line in CHANGELOG.md file about your PR please ? :)

[warmwaterkruik]

It looks really good ! I will make a test on a code-base I have at work to make sure everything is fine since there is a lot of impactful changes. And I'll merge that if it's good.

Could you add a line in CHANGELOG.md file about your PR please ? :)

thank you! I added the line to the changelog.