public function getFieldId($contentId, $fieldDefIdentifier)
    {
        $content = $this->contentService->loadContent($contentId);

        $contentType = $this->contentTypeService
            ->loadContentType($content->contentInfo->contentTypeId);

        $field = $contentType->getFieldDefinition($fieldDefIdentifier);

        if (!$field instanceof FieldDefinition) {
            throw new OutOfBoundsException(sprintf("ContentType does not contain field with identifier %s.", $fieldDefIdentifier));
        }

        return $field->id;
    }