feat(headers): add last-event-id header

Add a Last-Event-ID header to properly work with Server-Sent Events

Addresses # 723

src/header/common/last-event-id.rs

@@ -0,0 +1,30 @@
+header! {
+ /// `Last-Event-ID` header, defined in
+ /// [RFC3864](https://html.spec.whatwg.org/multipage/references.html#refsRFC3864)
+ ///
+ /// The `Last-Event-ID` header contains information about
+ /// the last event in an http interaction so that it's easier to
+ /// track of event state. This is helpful when working
+ /// with [Server-Sent-Events](http://www.html5rocks.com/en/tutorials/eventsource/basics/). If the connection were to be dropped, for example, it'd
+ /// be useful to let the server know what the last event you
+ /// recieved was.
+ ///
+ /// The spec is a String with the id of the last event, it can be
+ /// an empty string which acts a sort of "reset".
+ ///
+ /// # Example
+ /// ```
+ /// use hyper::header::{Headers, LastEventID};
+ ///
+ /// let mut headers = Headers::new();
+ /// headers.set(LastEventID("1".to_owned()));
+ /// ```
+ (LastEventID, "Last-Event-ID") => [String]
+
+ test_last_event_id {
+ // Initial state
+ test_header!(test1, vec![b""]);
+ // Own testcase
+ test_header!(test2, vec![b"1"], Some(LastEventID("1".to_owned())));
+ }
+}