chore: add an example of command to execute queries in runnin mysql container

[skip ci]

Author: php-coder

infra/docker/prod.yml

@@ -34,6 +34,9 @@ services:
       # NOTE: it's better to have credentials the same as in .github/workflows/integration-tests-mysql.yml
       # and src/main/resources/application-travis.properties
       # the generated root password will be printed to stdout (GENERATED ROOT PASSWORD: ...)
+      #
+      # Example:
+      # docker exec -it mystamps_db_1 mysql -u mystamps mystamps -psecret -e 'show tables'
       - MYSQL_RANDOM_ROOT_PASSWORD=true
       - MYSQL_USER=mystamps
       # FIXME: try to use a secret