[SOGo, Config, Update] Add SOGO_EXPIRE_SESSION to define default session timeout

generate_config.sh

@@ -250,6 +250,9 @@ IPV6_NETWORK=fd4d:6169:6c63:6f77::/64
 # mail_home is ~/Maildir
 MAILDIR_SUB=Maildir
 
+# SOGo session timeout in minutes
+SOGO_EXPIRE_SESSION=480
+
 EOF
 
 mkdir -p data/assets/ssl