Implement the Early-Data (RFC 8470) header

Closes hyperium#529

benches/src/header_map/basic.rs

@@ -551,6 +551,7 @@ const STD: &'static [HeaderName] = &[
     COOKIE,
     DNT,
     DATE,
+    EARLY_DATA,
     ETAG,
     EXPECT,
     EXPIRES,

src/header/mod.rs

@@ -116,6 +116,7 @@ pub use self::name::{
     COOKIE,
     DNT,
     DATE,
+    EARLY_DATA,
     ETAG,
     EXPECT,
     EXPIRES,

src/header/name.rs

@@ -485,6 +485,9 @@ standard_headers! {
     /// Contains the date and time at which the message was originated.
     (Date, DATE, b"date");
 
+    /// Indicates that the request has been conveyed in early data and that a client understands the 425 (Too Early) status code.
+    (EarlyData, EARLY_DATA, b"early-data");
+
     /// Identifier for a specific version of a resource.
     ///
     /// This header allows caches to be more efficient, and saves bandwidth, as

tests/header_map.rs

@@ -361,6 +361,7 @@ const STD: &'static [HeaderName] = &[
     COOKIE,
     DNT,
     DATE,
+    EARLY_DATA,
     ETAG,
     EXPECT,
     EXPIRES,

tests/header_map_fuzz.rs

@@ -297,6 +297,7 @@ fn gen_header_name(g: &mut StdRng) -> HeaderName {
         header::COOKIE,
         header::DNT,
         header::DATE,
+        header::EARLY_DATA,
         header::ETAG,
         header::EXPECT,
         header::EXPIRES,