* Represent a common File. Need to be extended by real Document
* You need to implement $vichUploadFileKey and the annotation of the $file to specify the mapping key inside it (defined also in config.yml -> vich_uploader)
*/
classAbstractFile
{
protected$vichUploadFileKey="default_file";
/**
* NOTE: This is not a mapped field of entity metadata, just a simple property.