Migrate ejabberd uploads to mod_s3_upload and Garage

In addition to installing and configuring the new module, this also
enables public access to the S3 API via `bucket-name.s3.kosmos.org` as
well as Web access on `bucket-name.web.s3.kosmos.org` (when enabled).

Also includes some drive-by improvements to Chef attribute naming and
usage.

Co-authored-by: Greg Karékinian <greg@karekinian.com>

site-cookbooks/kosmos-ejabberd/recipes/letsencrypt.rb

@@ -20,7 +20,7 @@ for domain in $RENEWED_DOMAINS; do
     cp "${RENEWED_LINEAGE}/fullchain.pem" /opt/ejabberd/conf/$domain.crt
     chown ejabberd:ejabberd /opt/ejabberd/conf/$domain.*
     chmod 600 /opt/ejabberd/conf/$domain.*
-    /opt/ejabberd-#{node["kosmos-ejabberd"]["version"]}/bin/ejabberdctl reload_config
+    /opt/ejabberd-#{node["ejabberd"]["version"]}/bin/ejabberdctl reload_config
     ;;
   esac
 done