* 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'.