The server may set this response header to set a custom browser location after a fragment update.
Without an X-Up-Location header Unpoly will set the browser location to the
requested URL. After a redirect the URL of the last request is used.
You only need to set X-Up-Location when you want to explicitly set a different URL.
When setting X-Up-Location it is recommended to also set X-Up-Method.
Example
X-Up-Location: /current-url
X-Up-Method: GET
