tg:// filename (?)
filename = dc_id + _ + document_id (?)
filename = volume_id + _ + local_id + . + jpg (?)
filename = md5(url) + . + extension (?)
filename = "" (?)
filename = dc_id + _ + document_id + _ + document_version + extension (?)

id (document id)
hash (access hash)
dc (dc id)
size (size)
mime (mime type)
name (document file name)