Allow more generic overrides for horizon

With this patch we allow for a more easy way of overriding some
of the values that may be used in other distros while maintainting
the default values if those values are not overriden.

The following values are introduced to be overriden:
conf:
  software:
    apache2:
      conf_dir:
      site_dir:
      mods_dir:
      binary:
      start_flags:
      a2enmod:
      a2dismod:

On which:
 * conf_dir: directory where to drop the config files
 * site_dir: directory where to drop the enabled virtualhosts
 * mods_dir: directory where to drop any mod configuration
 * binary: the binary to use for launching apache
 * start_flags: any flags that will be passed to the apache binary call
 * a2enmod: mods to enable
 * a2dismod: mods to disable

Notice that if there is no overrides given, it should not affect anything
and the templates will not be changed as the default values are set to what
they used to be as to not disrupt existing deployments.

Change-Id: If0fb9ab03aacfcd7087e753698880505571d0233

horizon/templates/bin/_horizon.sh.tpl

@@ -27,8 +27,17 @@ function start () {
   # wsgi/horizon-http needs open files here, including secret_key_store
   chown -R horizon ${SITE_PACKAGES_ROOT}/openstack_dashboard/local/
 
-  a2enmod rewrite
-  a2dismod status
+  {{- if .Values.conf.software.apache2.a2enmod }}
+    {{- range .Values.conf.software.apache2.a2enmod }}
+  a2enmod {{ . }}
+    {{- end }}
+  {{- end }}
+
+  {{- if .Values.conf.software.apache2.a2dismod }}
+    {{- range .Values.conf.software.apache2.a2dismod }}
+  a2dismod {{ . }}
+    {{- end }}
+  {{- end }}
 
   if [ -f /etc/apache2/envvars ]; then
      # Loading Apache2 ENV variables
@@ -53,11 +62,11 @@ function start () {
   /tmp/manage.py compress --force
   rm -rf /tmp/_tmp_.secret_key_store.lock /tmp/.secret_key_store
 
-  exec apache2 -DFOREGROUND
+  exec {{ .Values.conf.software.apache2.binary }} {{ .Values.conf.software.apache2.start_parameters }}
 }
 
 function stop () {
-  apachectl -k graceful-stop
+  {{ .Values.conf.software.apache2.binary }} -k graceful-stop
 }
 
 $COMMAND

horizon/templates/deployment.yaml

@@ -101,12 +101,12 @@ spec:
               subPath: manage.py
               readOnly: true
             - name: horizon-etc
-              mountPath: /etc/apache2/sites-enabled/000-default.conf
+              mountPath: {{ .Values.conf.software.apache2.site_dir }}/000-default.conf
               subPath: horizon.conf
               readOnly: true
             {{- if .Values.conf.horizon.security }}
             - name: horizon-etc
-              mountPath: /etc/apache2/conf-available/security.conf
+              mountPath: {{ .Values.conf.software.apache2.conf_dir }}/security.conf
               subPath: security.conf
               readOnly: true
             {{- end }}

horizon/values.yaml

@@ -57,6 +57,17 @@ network:
     port: 31000
 
 conf:
+  software:
+    apache2:
+      binary: apache2
+      start_parameters: -DFOREGROUND
+      site_dir: /etc/apache2/sites-enable
+      conf_dir: /etc/apache2/conf-enabled
+      mods_dir: /etc/apache2/mods-available
+      a2enmod:
+        - rewrite
+      a2dismod:
+        - status
   horizon:
     apache: |
       Listen 0.0.0.0:{{ tuple "dashboard" "internal" "web" . | include "helm-toolkit.endpoints.endpoint_port_lookup" }}