auto load authorization middlewhere when possible

lib/faraday/connection.rb

@@ -186,8 +186,7 @@ def #{method}(url = nil, body = nil, headers = nil, &block)
     #
     # Returns nothing.
     def basic_auth(login, pass)
-      headers[Faraday::Request::Authorization::KEY] =
-        Faraday::Request::BasicAuthentication.header(login, pass)
+      set_authorization_header(:basic_auth, login, pass)
     end
 
     # Public: Sets up the Authorization header with the given token.
@@ -204,8 +203,7 @@ def basic_auth(login, pass)
     #
     # Returns nothing.
     def token_auth(token, options = nil)
-      headers[Faraday::Request::Authorization::KEY] =
-        Faraday::Request::TokenAuthentication.header(token, options)
+      set_authorization_header(:token_auth, token, options)
     end
 
     # Public: Sets up a custom Authorization header.
@@ -227,8 +225,7 @@ def token_auth(token, options = nil)
     #
     # Returns nothing.
     def authorization(type, token)
-      headers[Faraday::Request::Authorization::KEY] =
-        Faraday::Request::Authorization.header(type, token)
+      set_authorization_header(:authorization, type, token)
     end
 
     # Internal: Traverse the middleware stack in search of a
@@ -395,6 +392,12 @@ def with_uri_credentials(uri)
         yield Utils.unescape(uri.user), Utils.unescape(uri.password)
       end
     end
+
+    def set_authorization_header(header_type, *args)
+      header = Faraday::Request.lookup_middleware(header_type).
+        header(*args)
+      headers[Faraday::Request::Authorization::KEY] = header
+    end
   end
 end