[Dovecot] Add extra.conf include to override Dovecot configuration changes

.gitignore

@@ -16,3 +16,4 @@ data/conf/rspamd/override.d/*
 !data/conf/nginx/dynmaps.conf
 !data/conf/nginx/site.conf
 data/conf/nginx/*.conf
+data/conf/dovecot/extra.conf

data/conf/dovecot/dovecot.conf

@@ -1,3 +1,6 @@
+# --------------------------------------------------------------------------
+# Please create a file "extra.conf" for persistent overrides to dovecot.conf
+# --------------------------------------------------------------------------
 auth_mechanisms = plain login
 #mail_debug = yes
 log_path = syslog
@@ -256,3 +259,4 @@ service imap-postlogin {
   unix_listener imap-postlogin {
   }
 }
+!include_try /usr/local/etc/dovecot/extra.conf