Requiring the user to input their password in order to unlock a device is not
always reasonable, so having an option to unlock the device using a key file
is a nice quality of life change.
* gnu/system/mapped-devices.scm (open-luks-device): Add #:key-file argument.
(luks-device-mapping-with-options): New procedure.
* doc/guix.texi (Mapped Devices): Describe the new procedure.
Change-Id: I1de4e045f8c2c11f9a94f1656e839c785b0c11c4
Signed-off-by: Ludovic Courtès <ludo@gnu.org>