fix: handle building the HTTP client proxy URI without authentication (#445)

* Fix http client proxy URI without authentication

* Add back missing 'proxy_prot' instance variable

Author: laka3000

lib/twilio-ruby/http/http_client.rb

@@ -11,10 +11,8 @@ class Client
       def initialize(proxy_prot = nil, proxy_addr = nil, proxy_port = nil, proxy_user = nil, proxy_pass = nil,
                      ssl_ca_file = nil, timeout: nil)
         @proxy_prot = proxy_prot
-        @proxy_addr = proxy_addr
-        @proxy_port = proxy_port
-        @proxy_user = proxy_user
-        @proxy_pass = proxy_pass
+        @proxy_path = "#{proxy_addr}:#{proxy_port}" if proxy_addr && proxy_port
+        @proxy_auth = "#{proxy_user}:#{proxy_pass}@" if proxy_pass && proxy_user
         @ssl_ca_file = ssl_ca_file
         @timeout = timeout
         @adapter = Faraday.default_adapter
@@ -27,9 +25,7 @@ def _request(request)
           f.adapter @adapter
           f.headers = request.headers
           f.basic_auth(request.auth[0], request.auth[1])
-          if @proxy_addr
-            f.proxy = "#{@proxy_prot}://#{@proxy_user}:#{@proxy_pass}@#{@proxy_addr}:#{@proxy_port}"
-          end
+          f.proxy = "#{@proxy_prot}://#{@proxy_auth}#{@proxy_path}" if @proxy_prot && @proxy_path
           f.options.open_timeout = request.timeout || @timeout
           f.options.timeout = request.timeout || @timeout
         end