new endpoints:
/services/<service_id>/move-to-folder
/services/<service_id>/move-to-folder/<target_template_folder_id>
* takes in a dict containing lists of `templates` and `folders` uuids.
* sets parent of templates and folders to the folder specified in the
URL. Or None, if there was no id specified.
* if any template or folder has a differen service id, then the whole
update fails
* if any folder is an ancestor of the target folder, then the whole
update fails (as that would cause a cyclical folder structure).
* the whole function is wrapped in a single `transactional` decorator,
so in case of error nothing will be saved.
d9aa220aa6