6 files declare their use of ResourceIdentifier

EntityAccessDeniedHttpException.php in core/modules/jsonapi/src/Exception/EntityAccessDeniedHttpException.php
EntityReferenceFieldNormalizer.php in core/modules/jsonapi/src/Normalizer/EntityReferenceFieldNormalizer.php
EntityResource.php in core/modules/jsonapi/src/Controller/EntityResource.php
JsonApiDocumentTopLevelNormalizer.php in core/modules/jsonapi/src/Normalizer/JsonApiDocumentTopLevelNormalizer.php
ResourceIdentifierNormalizer.php in core/modules/jsonapi/src/Normalizer/ResourceIdentifierNormalizer.php
ResourceIdentifierNormalizerTest.php in core/modules/jsonapi/tests/src/Unit/Normalizer/ResourceIdentifierNormalizerTest.php

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