pub fn parse_endpoint(endpoint: &str) -> Result<Url, String>Expand description
endpoint as a push subscription’s (decision 3), in the form it is
stored, looked up and sent to (the review’s A2), or why it cannot be one.
The push services’ endpoints are https URLs on their own domain names
at the default port; anything else is refused before it is stored, and
the address it resolves to is checked again on every send (kernel spec
§7.1).