* gnu/services/base.scm (<guix-publish-configuration>): New record
type.
(guix-publish-dmd-service): New procedure.
(%guix-publish-accounts, guix-publish-service-type): New variables.
(guix-publish-service): New procedure.
* doc/guix.texi (Invoking guix publish): Add xref to
'guix-publish-service' anchor.
(Base Services): Document 'guix-publish-service'.