Ignore deprecation warning for crypto:sha/1 for now

We can change this call when we start supporting only R16B+,
which may happen when R17B is released or some time before.

src/cowboy_websocket.erl

@@ -19,6 +19,10 @@
 -module(cowboy_websocket).
 -behaviour(cowboy_sub_protocol).
 
+%% Ignore the deprecation warning for crypto:sha/1.
+%% @todo Remove when we support only R16B+.
+-compile({nowarn_deprecated_function, {crypto, sha, 1}}).
+
 %% API.
 -export([upgrade/4]).
 
@@ -176,6 +180,7 @@ upgrade_error(Req, Env) ->
 websocket_handshake(State=#state{
 			transport=Transport, key=Key, deflate_frame=DeflateFrame},
 		Req, HandlerState) ->
+	%% @todo Change into crypto:hash/2 for R17B+ or when supporting only R16B+.
 	Challenge = base64:encode(crypto:sha(
 		<< Key/binary, "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" >>)),
 	Extensions = case DeflateFrame of