services: certbot: Add default value and description.

* gnu/services/certbot.scm (certbot-service-type)
[default-value, description]: New fields.
* po/packages/POTFILES.in: Add it.

services: cgit, git-daemon: Add description and default value.

* gnu/services/version-control.scm (git-daemon-service-type)
[description, default-value]: New fields.
(cgit-service-type)[default-value]: New field.
* po/packages/POTFILES.in: Add version-control.scm.

services: Add Git HTTP(S) service support.

* doc/guix.texi (Version Control Services): Add documentation on the HTTP
backend for git.
* gnu/services/version-control.scm (<git-http-configuration>): New data type.
(git-http-nginx-location-configuration): New helper function.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

services: Add certbot service.

* gnu/services/certbot.scm: New file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Add new file.
* doc/guix.texi (Certificate Services): New section.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

services: xorg: Remove WindowMaker as a default fallback.

* gnu/services/xorg.scm (xinitrc)[builder](system-profile)
(user-profile): New variables.
(xsession-command, find-session): New procedures.
When FALLBACK-SESSION is #f, find a valid session at run time.
* doc/guix.texi (X Window): Adjust accordingly, and insist that one
or more window managers must be installed.

services: xorg: Document 'slim-configuration' and deprecate 'slim-service'.

* gnu/services/xorg.scm (<slim-configuration>): Provide default values
for all fields.
(slim-service-type)[default-value]: New field.
* doc/guix.texi (X Window): Remove 'slim-service' documentation.
Document 'slim-service-type' and 'slim-configuration'.
* gnu/services/desktop.scm (%desktop-services): Use 'slim-service-type'.

services: slim: Remove unused 'bash' configuration field.

* gnu/services/xorg.scm (<slim-configuration>)[bash]: Remove.
(slim-service): Adjust accordingly.

services: xorg: Allow users to specify a list of modules.

* gnu/services/xorg.scm (%default-xorg-fonts): New variable.
(xorg-configuration-file): Add #:modules and #:fonts.  Rewrite to return
a 'computed-file' that honors MODULES and FONTS.
(xorg-wrapper): Pass #:modules to 'xorg-configuration-file'.
(xorg-start-command): Add #:fonts.  Pass #:fonts and #:modules to
'xorg-configuration-file'.
* doc/guix.texi (X Window): Adjust documentation of 'xorg-start-command'
and 'xorg-configuration-file'.

services: configuration: Show default values of list types.

* doc/guix.texi (Messaging Services): Regenerate it.
* gnu/services/configuration.scm (show-default?): Check VAL rather than DEFAULT.
* gnu/services/messaging.scm (show-default?): Check VAL rather than DEFAULT.
(prosody-configuration)[modules-enabled]: Remove default value from docstring.

services: desktop: Create /var/run/udisks2 for the udisks service.

* gnu/services/desktop.scm (%udisks-activation): New variable.
  (udisks-service-type)[extensions]: Extend the activation service type with
  %udisks-activation.

services: prosody: Add support for disable-sasl-mechanisms.

* doc/guix.texi (Messaging Services): Update accordingly.
* gnu/services/messaging.scm (prosody-configuration)[disable-sasl-mechanisms]:
New field.

services: prosody: Allow to add raw content to the config file.

* doc/guix.texi (Messaging Services): Update accordingly.
* gnu/services/messaging.scm (prosody-configuration)[raw-content]: New field.
(raw-content?, serialize-raw-content): New procedures.

services: prosody: Add support for http-max-content-size.

* doc/guix.texi (Messaging Services): Update accordingly.
* gnu/services/messaging.scm (prosody-configuration)[http-max-content-size]:
New field.

services: prosody: Add support for http-external-url.

* doc/guix.texi (Messaging Services): Update accordingly.
* gnu/services/messaging.scm (prosody-configuration)[http-external-url]: New
field.

services: prosody: Adapt to Prosody 0.10.0.

* doc/guix.texi (Messaging Services): Add "mam" as a module example.  Document
'prosodyctl check'.  Replace 'prosodyctl cert request' with 'prosodyctl cert
import'.  Regenerate it.
* gnu/services/messaging.scm (serialize-module-list): Remove "posix" from the
default modules list because it is now automatically loaded.
(ssl-configuration)[key, certificate]: Remove them because they are now
automatically located.  Fix their docstrings.
(%default-modules-enabled): Add "carbons" and "blocklist".
(prosody-configuration)[certificates]: Set default directory from which
certificates/keys will be automatically located.

services: dicod: Run in a container.

* gnu/services/dict.scm (dicod-shepherd-service): Add
'with-imported-modules' form and 'modules' field.  Use
'make-forkexec-constructor/container' instead of
'make-forkexec-constructor'.

services: guix: Remove dependency on 'lsof'.

This is a followup to b8f59cdc20e9d83ce63523ef917e95fcee07f134:
'list-runtime-roots' no longer depends on 'lsof'.

* gnu/services/base.scm (<guix-configuration>)[lsof]: Remove.
(guix-shepherd-service): Adjust accordingly.
* doc/guix.texi (Base Services): Adjust accordingly.
* gnu/system.scm (%base-packages): Remove LSOF.

gnu: service: Update comment.

* gnu/services/base.scm (guix-activation): Update comment.

services: gdm: Add environment variables.

While not an optimal solution (see comment), this makes GDM functional.

* gnu/services/xorg.scm (gdm-shepherd-service): Set PATH and XDG_DATA_DIRS
environment variables.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>

services: Add 'description' fields.

* gnu/services/admin.scm (rottlog-service-type)
(tailon-service-type): Add 'description' field.
* gnu/services/audio.scm (mpd-service-type): Likewise.
* gnu/services/avahi.scm (avahi-service-type): Likewise.
* gnu/services/ssh.scm (lsh-service-type)
(openssh-service-type, dropbear-service-type): Likewise.