Add update-guest service
https://gitlab.com/LibreFoodPantry/modules/visitmodule-tp/checkout/Plan/-/issues/28
This created the service to update guests, which will not work until the endpoint is created. Nevertheless, this should be usable as soon as that is done. I made an educated guess on what the endpoint will need to be. This may need to be changed when it is implemented.
Edited by James Young