Issue #3022475 by e0ipso: Drop support for JSON:API 2.x in JSON:API Extras 2.x

composer.json

jsonapi_extras.services.yml

src/Entity/JsonapiResourceConfig.php

src/EntityToJsonApi.php

src/JsonapiExtrasServiceProvider.php

src/Normalizer/EntityNormalizerTrait.php

src/ResourceType/ConfigurableResourceTypeRepository.php

src/SerializerDecorator.php

tests/src/Functional/JsonExtrasApiFunctionalTest.php

tests/src/Kernel/Controller/EntityResourceTest.php

tests/src/Kernel/EntityToJsonApiTest.php