Fixes #32192 - Monkey patch restclient to unescape proxy credentials

Restclient as of version 2.1.0 uses provided credentials stored in a proxy URI
object verbatim. If the credentials are escaped as they should be, then this
leads to errors when we try to use the credentials because restclient sends the
escaped form.

There is a PR[1] in upstream restclient, which addresses this issue, but last
movement there was in October 2018. ManageIQ folks decided to monkey patch
restclient when they ran into the same issue, this commit is a loose adaptation
of the original[1] and ManageIQ patches[2].

[1] - rest-client/rest-client#665
[2] - ManageIQ/manageiq#18105

lib/foreman/http_proxy/rest_client_extension.rb

@@ -8,6 +8,23 @@ def proxy_uri
         end
         super
       end
+
+      def net_http_object(hostname, port)
+        p_uri = proxy_uri
+
+        if p_uri.nil?
+          # no proxy set
+          Net::HTTP.new(hostname, port)
+        elsif !p_uri
+          # proxy explicitly set to none
+          Net::HTTP.new(hostname, port, nil, nil, nil, nil)
+        else
+          proxy_pass = p_uri.password ? CGI.unescape(p_uri.password) : nil
+          proxy_user = p_uri.user ? CGI.unescape(p_uri.user) : nil
+          Net::HTTP.new(hostname, port,
+                        p_uri.hostname, p_uri.port, proxy_user, proxy_pass)
+        end
+      end
     end
   end
 end