same functionality as crypto_parameters, except it keeps the file
descriptor passed as "keyfd" open (and seeks to the beginning after
reading), if one is given.
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>
Add a new module containing key-related functions and schemata from all
over, code moved is not changed as much as possible.
Requires adapting some 'use' statements across proxmox-backup-client and
putting the XDG helpers quite cozily into proxmox_client_tools/mod.rs
Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>