Allow passing extra options to the 'cryptsetup open' command.
* gnu/system/mapped-devices.scm (luks-device-mapping-with-options):
[#:extra-options]: New argument.
(open-luks-device): Use it.
(check-luks-device): Validate it.
* doc/guix.texi (Mapped Devices): Document it.
* gnu/tests/install.scm (%test-encrypted-root-extra-options-os): New
test for it, as well as the previously untested #:allow-discards?
option.
(%encrypted-root-extra-options-os): New os declaration for the test.
Change-Id: I265a431efb0c81ed7cfc984344c6b8a4cc2f1624
Signed-off-by: Ludovic Courtès <ludo@gnu.org>