Issue #3410651: Add missing service definition for policy helper

csp.services.yml

@@ -2,6 +2,10 @@ services:
   csp.nonce:
     class: Drupal\csp\Nonce
 
+  csp.policy_helper:
+    class: Drupal\csp\PolicyHelper
+    arguments:
+      - '@csp.nonce'
   csp.response_listener:
     class: Drupal\csp\EventSubscriber\ResponseCspSubscriber
     arguments:
@@ -12,6 +16,7 @@ services:
       - '@csp.nonce'
     tags:
       - { name: event_subscriber }
+
   csp.library_policy_builder:
     class: Drupal\csp\LibraryPolicyBuilder
     arguments: