* gnu/system/accounts.scm (sexp->user-group, sexp->user-account): New
procedures.
* gnu/system/shadow.scm (account-activation): Call them in the arguments
to 'activate-users+groups'.
(account-shepherd-service): Likewise.
* gnu/build/activation.scm (activate-users+groups): Expect a list of
<user-account> and a list of <user-group>. Replace uses of 'match' on
tuples with calls to record accessors.
(activate-user-home): Likewise.
The (gnu system accounts) module is meant to be used both on the build-
and on the host-side.
* gnu/system/shadow.scm <top level>: Call 'default-shell'.
(<user-account>, <user-group>): Move to...
* gnu/system/accounts.scm: ... here. New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add system/accounts.scm.
Maxim Cournoyer
Ludovic Courtès