Client Side
When we fetch an RSC payload, it's going to have our action in there.
react-server-dom-esm/client needs to be told what to do when the action is
called.This is where the
callServer function comes in. You pass that as an option
to createFromFetch and whenever an action is called, it will call your
function. It's your job to send the action to the server and return the
return value.At this stage, our server doesn't handle the POST request yet, but you can
check the Network devtools to see that the request is being sent properly.