As it turns out, even caching only by request has consequences e.g. when one installs xolp from scratchDisabl caching and prepare the statement instead
Make fs::get_folder_contents private: this api is only used internally to the file-storage over the codebase and its documentation suggests that it should be used with caution
Complete proc coverage, which required some heavier refactoring of the tests: it is not trivial otherwise to simulate subscription to an arbitrary object