Similarly to method _binary_set_headers, when we serve an attachment
(e.g. image) where an unique is present in URL we add a long time of cache.
We considere that the hash will be changed if attachment is updated, so
while we ask for same checksum, lets the browser return the cached response.
closesodoo/odoo#48653
Signed-off-by: Christophe Simonis <chs@odoo.com>