Add fake telegram "middle-proxy" server and http config server implementations

And make it possible to make proxy connect to it

src/mtp_config.erl

@@ -168,11 +168,13 @@ update(State, _) ->
     end.
 
 update_key(Tab) ->
-    {ok, Body} = http_get(?SECRET_URL),
+    Url = application:get_env(mtproto_proxy, proxy_secret_url, ?SECRET_URL),
+    {ok, Body} = http_get(Url),
     true = ets:insert(Tab, {key, list_to_binary(Body)}).
 
 update_config(Tab) ->
-    {ok, Body} = http_get(?CONFIG_URL),
+    Url = application:get_env(mtproto_proxy, proxy_config_url, ?CONFIG_URL),
+    {ok, Body} = http_get(Url),
     Downstreams = parse_config(Body),
     update_downstreams(Downstreams, Tab),
     update_ids(Downstreams, Tab).

src/mtproto_proxy.app.src

@@ -63,12 +63,17 @@
 
         %% Should be module with function `notify/4' exported.
         %% See mtp_metric:notify/4 for details
-        %% {metric_backend, my_metric_backend}
+        %% {metric_backend, my_metric_backend},
 
         %% User-space recv socket buffer sizes. Set to higher if you have
         %% enough RAM
         %% {upstream_socket_buffer_size, 51200},   %50kb
-        %% {downstream_socket_buffer_size, 512000}   %500kb
+        %% {downstream_socket_buffer_size, 512000},   %500kb
+
+        %% Where to fetch telegram proxy configuration
+        %% Mostly used to testing
+        %% {proxy_secret_url, "https://core.telegram.org/getProxySecret"},
+        %% {proxy_config_url, "https://core.telegram.org/getProxyConfig"},
        ]},
   {modules, []},
 

src/mtproto_proxy_app.erl

@@ -15,7 +15,7 @@
 %% API
 %%====================================================================
 start(_StartType, _StartArgs) ->
-    Res = mtproto_proxy_sup:start_link(),
+    Res = {ok, _} = mtproto_proxy_sup:start_link(),
     io:format("+++++++++++++++++++++++++++++++++++++++~n"
               "Erlang MTProto proxy by @seriyps https://github.com/seriyps/mtproto_proxy~n"
               "Sponsored by and powers @socksy_bot~n"),