services: nginx: Add 'shepherd-requirement' configuration field.

* gnu/services/web.scm (<nginx-configuration>)[shepherd-requirement]:
New field.
(nginx-shepherd-service): Honor it.
* doc/guix.texi (Web Services): Document it.

1 files changed, 8 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index d573695e72..20abfee772 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -28841,6 +28841,14 @@ types, or alternatively, a config file can be provided.
 @item @code{nginx} (default: @code{nginx})
 The nginx package to use.
 
+@item @code{shepherd-requirement} (default: @code{'()})
+This is a list of symbols naming Shepherd services the nginx service
+will depend on.
+
+This is useful if you would like @command{nginx} to be started after a
+back-end web server or a logging service such as Anonip has been
+started.
+
 @item @code{log-directory} (default: @code{"/var/log/nginx"})
 The directory to which NGinx will write log files.