Introduction of 12.0.0 upgrade scripts due to #7043

Also add script to remove tenant and option to use proxysql

docs/PacketFence_Upgrade_Guide.asciidoc

@@ -1856,6 +1856,89 @@ recommend you to set a value for this attribute.
 By doing this, `pfpki` will use email addresses defined in PKI templates to
 notify about next certificates expirations for certificates without emails.
 
+== Upgrading from a version prior to 12.0.0
+
+=== Automation of upgrades for standalone servers
+
+Upgrades are now automated for standalone servers starting from PacketFence 11.0.0.
+Follow instructions related to
+<<PacketFence_Installation_Guide.asciidoc#_automation_of_upgrades,automation
+of upgrades>>.
+
+=== Note for cluster upgrades
+
+If you use a cluster, their upgrade isn't yet automated so you will need to follow the instructions in this section to upgrade the configuration and database schema.
+
+==== Configuration upgrade
+
+[source,bash]
+----
+/usr/local/pf/addons/upgrade/to-12.0-remove-tenant.pl
+/usr/local/pf/addons/upgrade/to-12.0-use-proxysql.pl
+----
+
+If you use a Syslog Forwarder to send log files to a remote Syslog server, you should run following script:
+
+[source,bash]
+----
+/usr/local/pf/addons/upgrade/to-12.0-rename-log-files.pl
+----
+
+==== Database schema
+
+Changes have been made to the database schema. You will need to update it accordingly.
+An SQL upgrade script has been provided to upgrade the database from the 11.2 schema to 12.0.
+
+To upgrade the database schema, run the following command:
+
+[source,bash]
+----
+# Only run this for cluster upgrades
+mysql -u root -p pf -v < /usr/local/pf/db/upgrade-11.2-12.0.sql
+----
+
+=== Log files names updated
+
+The name of some log files have changed. You can find a list below:
+
+.Mapping between old and new log files
+|===
+|Service |Old log file(s) |New log file(s)
+
+|MariaDB
+|mariadb_error.log
+|mariadb.log
+
+|httpd.aaa (Apache requests)
+|httpd.aaa.access and httpd.aaa.error
+|httpd.apache
+
+|httpd.collector (Apache requests)
+|httpd.collector.log and httpd.collector.error
+|httpd.apache
+
+|httpd.portal (Apache requests)
+|httpd.portal.access, httpd.portal.error, httpd.portal.catalyst
+|httpd.apache
+
+|httpd.proxy (Apache requests)
+|httpd.proxy.error and httpd.proxy.access
+|httpd.apache
+
+|httpd.webservices (Apache requests)
+|httpd.webservices.error and httpd.webservices.access
+|httpd.apache
+
+|api-frontend (Apache requests)
+|httpd.api-frontend.access 
+|httpd.apache
+
+|HAProxy (all services)
+|/var/log/syslog or /var/log/messages
+|haproxy.log
+|===
+
+
 == Upgrading from a version prior to X.Y.Z
 
 === Database schema