feat: add environment variables for session metadata and memcached server ID

Author: voronkovich

docs/reference/configuration.md

@@ -832,6 +832,8 @@ Track guest session metadata.
 
 Default: `true`
 
+Env: `JOOMLA_SESSION_METADATA_FOR_GUEST`
+
 ### session_filesystem_path
 
 Path for session files.
@@ -860,6 +862,8 @@ Memcached server identity.
 
 Default: `joomla_cms`
 
+Env: `JOOMLA_SESSION_MEMCACHED_SERVER_ID`
+
 ### session_redis_server_host
 
 Redis server hostname or IP address.
@@ -924,13 +928,13 @@ JOOMLA_SESSION_HANDLER=redis
 JOOMLA_SESSION_LIFETIME=60
 JOOMLA_SESSION_SHARED=true
 JOOMLA_SESSION_METADATA=false
-# session_metadata_for_guest is not available as an environment variable
+JOOMLA_SESSION_METADATA_FOR_GUEST=false
 
 JOOMLA_SESSION_FILESYSTEM_PATH=/var/www/sessions
 
 JOOMLA_SESSION_MEMCACHED_SERVER_HOST=127.0.0.1
 JOOMLA_SESSION_MEMCACHED_SERVER_PORT=22122
-# session_memcached_server_id is not available as an environment variable
+JOOMLA_SESSION_MEMCACHED_SERVER_ID=joomla
 
 JOOMLA_SESSION_REDIS_SERVER_HOST=127.0.0.1
 JOOMLA_SESSION_REDIS_SERVER_PORT=9736