Add endpoint and service to create Leads

We need to create Leads when customers are requesting a trial for
GL.com. In order to do it we're going to use a service that will call a
custom endpoint on the subscription portal.

config/routes/trial.rb

 # frozen_string_literal: true
 
-resources :trials, only: [:new, :create]
+resources :trials, only: [:new] do
+  collection do
+    post :create_lead
+  end
+end