Redirect health check monitoring to /ping

We previously optimized the SQL queries, so that anonymous users without any cookie sent no longer result in a database query. This is generally awesome, but it also allows our health check monitoring to pass even when no database connection can be established.

app/controllers/application_controller.rb

@@ -7,6 +7,7 @@ class ApplicationController < ActionController::Base
   MEMBER_ACTIONS = %i[destroy edit show update].freeze
   RENDER_HOST = CodeOcean::Config.new(:code_ocean).read[:render_host]
   LEGAL_SETTINGS = CodeOcean::Config.new(:code_ocean).read[:legal] || {}
+  MONITORING_USER_AGENT = Regexp.compile(/updown\.io/).freeze
 
   before_action :deny_access_from_render_host
   after_action :verify_authorized, except: %i[welcome]
@@ -134,6 +135,7 @@ class ApplicationController < ActionController::Base
 
   def welcome
     # Show root page
+    redirect_to ping_index_path if MONITORING_USER_AGENT.match?(request.user_agent)
   end
 
   def load_embed_options