private function resolveNewFieldDefinitionIdentifier(
        ContentTypeDraft $contentTypeDraft,
        int $startIndex,
        string $fieldTypeIdentifier
    ): string {
        $fieldDefinitionIdentifiers = array_map(function (FieldDefinition $fieldDefinition) {
            return $fieldDefinition->identifier;
        }, $contentTypeDraft->getFieldDefinitions());

        do {
            $fieldDefinitionIdentifier = sprintf('new_%s_%d', $fieldTypeIdentifier, ++$startIndex);
        } while (in_array($fieldDefinitionIdentifier, $fieldDefinitionIdentifiers, true));

        return $fieldDefinitionIdentifier;
    }