new: [mariadb] allow easy access to standard full priviledged ``mysql`` command

mariadb/hooks/init

@@ -57,3 +57,10 @@ EOF
 
     info "New root password for mysql. "
 fi
+
+init-config-add "\
+$MASTER_BASE_SERVICE_NAME:
+  volumes:
+      - '$HOST_DB_PASSFILE:/root/.my.cnf'
+"
+