feat(headers): Add From header field

src/header/common/from.rs

@@ -0,0 +1,18 @@
+header! {
+    #[doc="`From` header, defined in [RFC7231](http://tools.ietf.org/html/rfc7231#section-5.5.1)"]
+    #[doc=""]
+    #[doc="The `From` header field contains an Internet email address for a"]
+    #[doc="human user who controls the requesting user agent.  The address ought"]
+    #[doc="to be machine-usable."]
+    #[doc="# ABNF"]
+    #[doc="```plain"]
+    #[doc="From    = mailbox"]
+    #[doc="mailbox = <mailbox, see [RFC5322], Section 3.4>"]
+    #[doc="```"]
+    // FIXME: Maybe use mailbox?
+    (From, "From") => [String]
+
+    test_from {
+        test_header!(test1, vec![b"webmaster@example.org"]);
+    }
+}