23 files declare their use of ResourceType in JSON:API 8

ConfigEntityNormalizer.php in src/Normalizer/ConfigEntityNormalizer.php

ConfigEntityNormalizerTest.php in tests/src/Unit/Normalizer/ConfigEntityNormalizerTest.php

CountableResourceType.php in tests/modules/jsonapi_test_collection_count/src/ResourceType/CountableResourceType.php

EntityNormalizer.php in src/Normalizer/EntityNormalizer.php

EntityNormalizerValueTest.php in tests/src/Unit/Normalizer/Value/EntityNormalizerValueTest.php

EntityReferenceFieldNormalizer.php in src/Normalizer/EntityReferenceFieldNormalizer.php

EntityReferenceFieldNormalizerTest.php in tests/src/Unit/Normalizer/EntityReferenceFieldNormalizerTest.php

EntityResource.php in src/Controller/EntityResource.php

EntityResourceTest.php in tests/src/Kernel/Controller/EntityResourceTest.php

EntryPoint.php in src/Controller/EntryPoint.php

FieldResolver.php in src/Context/FieldResolver.php

JsonApiDocumentTopLevelNormalizer.php in src/Normalizer/JsonApiDocumentTopLevelNormalizer.php

JsonApiDocumentTopLevelNormalizerTest.php in tests/src/Unit/Normalizer/JsonApiDocumentTopLevelNormalizerTest.php

JsonApiDocumentTopLevelNormalizerValueTest.php in tests/src/Unit/Normalizer/Value/JsonApiDocumentTopLevelNormalizerValueTest.php

JsonApiParamEnhancerTest.php in tests/src/Unit/Routing/JsonApiParamEnhancerTest.php

LinkManager.php in src/LinkManager/LinkManager.php

RelationshipItemNormalizerValueTest.php in tests/src/Unit/Normalizer/Value/RelationshipItemNormalizerValueTest.php

RelationshipNormalizerValueTest.php in tests/src/Unit/Normalizer/Value/RelationshipNormalizerValueTest.php

RequestHandler.php in src/Controller/RequestHandler.php

ResourceResponseValidatorTest.php in tests/src/Unit/EventSubscriber/ResourceResponseValidatorTest.php

ResourceTypeRepositoryTest.php in tests/src/Kernel/ResourceType/ResourceTypeRepositoryTest.php

Routes.php in src/Routing/Routes.php

RoutesTest.php in tests/src/Unit/Routing/RoutesTest.php