Track user IDs in Sentry

When sending errors to Sentry this allows us to track which user was
logged in at the time of the error, helping us to investigate issues.
Only the anonymised user ID will be sent to Sentry rather than any
personally identifiable information.

Author: thomasleese

app/controllers/application_controller.rb

@@ -14,6 +14,7 @@ class ApplicationController < ActionController::Base
   before_action :set_service_guide_url
   before_action :set_show_navigation
   before_action :set_privacy_policy_url
+  before_action :set_sentry_user
   before_action :authenticate_basic
 
   after_action :verify_policy_scoped, if: -> { Rails.env.local? }
@@ -75,4 +76,8 @@ def set_service_guide_url
   def set_privacy_policy_url
     @privacy_policy_url = nil
   end
+
+  def set_sentry_user
+    Sentry.set_user(id: current_user&.id)
+  end
 end