Add a new impersonate sample

samples/cli/lib/samples/gmail.rb

@@ -120,5 +120,38 @@ module Samples
         end
       end
     end
+
+
+    desc 'impersonate and update email signature', 'Update the email signature of another user'
+    method_option :impersonated_email, type: :string, required: true
+    def update_email_signature(new_signature_content)
+      gmail = Gmail::GmailService.new
+
+      # You can download a client_secret.json from the service account page
+      # of your developer's console
+
+      attrs = {
+        json_key_io: 'client_secret.json',
+        scope: [ Gmail::AUTH_GMAIL_SETTINGS_BASIC ]
+      }
+
+      auth = Google::Auth::ServiceAccountCredentials.make_creds(attrs)
+      impersonate_auth = auth.dup
+      impersonate_auth.sub = impersonated_email
+
+      user_id = impersonated_email
+      send_as_email = update_user_setting_send_as
+
+
+      gmail.authorization = impersonate_auth
+
+      send_as_object = {"signature": new_signature_content}
+      # options: {} is necessary for method to be called correctly.
+      result = service.patch_user_setting_send_as(user_id, send_as_email, send_as_object, options: {})
+
+
+      puts "signature of #{impersonated_email} is now: #{result.signature}"
+    end
+
   end
 end