JsonApiServerImplementation 'final'`, doesn't allow custom implementations

[GeoSot]

JsonApiServerImplementation class is a simple DTO that keeps jsonapi server information.
There are cases, where some schemas need to declare some profiles etc. Unfortunately, the usage of final keyword, prevents any extension in order to support profile & extension properties.
It would be fine to either remove the final keyword, or support the extra properties JSON:API defines

json-api/src/JsonApiServerImplementation.php

Line 10 in 5c7f28b

final class JsonApiServerImplementation implements JsonSerializable

[GeoSot]

@timacdonald Can you help fixing this or propose a way in order to open a PR?
Any help will be appreciated

[timacdonald]

I would say that we should add support for those properties on the JsonApiServerImplementation class the package ships with.