Fix the webcal protocol when running behind a reverse proxy (#3679)

* Try to fix the webcal protocol when running behind a reverse proxy

* Rework for setting the webcal subscription link

* Remove '#' from href for webcal link

* Grunt

* Clean url (trim everything after 'calendar')

Need to run grunt again ofc

* Revert "Clean url (trim everything after 'calendar')"

This reverts commit cb6b241b0953ff5f43ca1826c6231c878ec95fee.

* Optional trailing slash in /calendar handler.

* Fix calendar handler

pass *args, **kwargs to get()