JSON:API data parser

Issue #3035777 on drupal.org by robin.ingelbrecht.

So I'm currently in the process of creating a custom data parser for JSON:API format. I came a cross different issues when using the default JSON data parser:

• Paging
• Relationships & included data

I could improve this by caching the result of the response in 'nextUrls()' so we don't have to execute the request again in 'getSourceData()'. But I first want to know if this data parser is a good idea :)

Maybe we could add this as a default data parser in this module?