Implement authorization header parsing

Basic HTTP authorization according to RFC 2617 is implemented.
Added an example of its usage with REST handler.

examples/basic_auth/src/toppage_handler.erl

@@ -0,0 +1,32 @@
+%% Feel free to use, reuse and abuse the code in this file.
+
+%% @doc Basic authorization Hello world handler.
+-module(toppage_handler).
+
+-export([init/3]).
+-export([content_types_provided/2]).
+-export([is_authorized/2]).
+-export([hello_to_text/2]).
+
+init(_Transport, _Req, []) ->
+	{upgrade, protocol, cowboy_rest}.
+
+
+is_authorized(Req, S) ->
+	{ok, Auth, Req1} = cowboy_req:parse_header(<<"authorization">>, Req),
+	case Auth of
+		{<<"basic">>, {User = <<"Alladin">>, <<"open sesame">>}} ->
+			{true, Req1, User};
+		_ ->
+			{{false, <<"Restricted">>}, Req1, S}
+	end.
+
+content_types_provided(Req, State) ->
+	{[
+		{<<"text/plain">>, hello_to_text}
+	], Req, State}.
+
+
+hello_to_text(Req, User) ->
+	{<< <<"Hello, ">>/binary, User/binary, <<"!\n">>/binary >>, Req, User}.
+