feat: add possibility to deploy/update backup proxy

sample.xo-install.cfg

@@ -1,18 +1,22 @@
 # Optional user that runs the service
 # default: root
+# no effect to Xen Orchestra proxy
 #XOUSER=
 
 # Optional parameter if running as non privileged user to use sudo when mounting/umounting shares inside Xen Orchestra
 # no effect if XOUSER is root
 # options true/false
+# no effect to Xen Orchestra proxy
 #USESUDO=false
 
 # Optional parameter to generate sudoers config when missing completely if USESUDO is set to true
 # no effect if XOUSER is root
 # options true/false
+# no effect to Xen Orchestra proxy
 #GENSUDO=false
 
 # Port number where xen-orchestra service is bound
+# no effect to Xen Orchestra proxy
 PORT="80"
 
 # Base dir for installation and future updates
@@ -25,6 +29,7 @@ SELFUPGRADE=true
 # Xen Orchestra configuration file is stored in XOUSER's home directory ($HOME/.config/xo-server/config.toml) and by default will be overwritten with every update done by this script.
 # You may disable this if you edit configuration by hand and don't want an update to overwrite it. Note that some of the options defined here won't be applied even if changed if this is set to false.
 # options: true/false
+# no effect to Xen Orchestra proxy
 CONFIGUPDATE=true
 
 # Location of Xen Orchestra repository where source code is fetched
@@ -65,6 +70,8 @@ ARCH_CHECK="true"
 # Define the number of previous successful installations you want to keep. Needs to be at least 1. Determines how far the rollback feature can be used.
 PRESERVE="3"
 
+# certificate settings have no effect to Xen Orchestra proxy, it'll generate it's own self-signed certificates always
+
 # Location of pem certificate/key files. Installation will automatically configure HTTPS if these are defined. Remember to change PORT variable as well.
 #PATH_TO_HTTPS_CERT=$INSTALLDIR/xo.crt
 #PATH_TO_HTTPS_KEY=$INSTALLDIR/xo.key