Add structured attributes

Signed-off-by: Fabio José <fabiojose@gmail.com>

lib/bindings/http/constants.js

@@ -16,5 +16,16 @@ module.exports = {
     TIME              : "ce-time",
     SCHEMA_URL        : "ce-schemaurl",
     EXTENSIONS_PREFIX : "ce-"
+  },
+
+  STRUCTURED_ATTRS_02 : {
+    TYPE         : "type",
+    SPEC_VERSION : "specversion",
+    SOURCE       : "source",
+    ID           : "id",
+    TIME         : "time",
+    SCHEMA_URL   : "schemaurl",
+    CONTENT_TYPE : "contenttype",
+    DATA         : "data"
   }
 };