Refactor Policy Enforcer to Policy Checker

- Renamed the `PolicyEnforcer` interface and related implementations to `PolicyChecker` for clarity and consistency.
- Updated configuration keys in YAML files to reflect the new `checkPolicy` terminology.
- Adjusted related code, tests, and documentation to support the new naming convention and ensure compatibility.
- Enhanced comments and examples for the `checkPolicy` configuration to improve usability.

core/module/handler/stdHandler.go

@@ -35,7 +35,7 @@ type stdHandler struct {
 	registry         definition.RegistryLookup
 	km               definition.KeyManager
 	schemaValidator  definition.SchemaValidator
-	policyEnforcer   definition.PolicyEnforcer
+	policyChecker    definition.PolicyChecker
 	router           definition.Router
 	publisher        definition.Publisher
 	transportWrapper definition.TransportWrapper
@@ -319,7 +319,7 @@ func (h *stdHandler) initPlugins(ctx context.Context, mgr PluginManager, cfg *Pl
 	if h.transportWrapper, err = loadPlugin(ctx, "TransportWrapper", cfg.TransportWrapper, mgr.TransportWrapper); err != nil {
 		return err
 	}
-	if h.policyEnforcer, err = loadPlugin(ctx, "PolicyEnforcer", cfg.PolicyEnforcer, mgr.PolicyEnforcer); err != nil {
+	if h.policyChecker, err = loadPlugin(ctx, "PolicyChecker", cfg.PolicyChecker, mgr.PolicyChecker); err != nil {
 		return err
 	}
 
@@ -354,8 +354,8 @@ func (h *stdHandler) initSteps(ctx context.Context, mgr PluginManager, cfg *Conf
 			s, err = newValidateSchemaStep(h.schemaValidator)
 		case "addRoute":
 			s, err = newAddRouteStep(h.router)
-		case "policyEnforcer":
-			s, err = newEnforcePolicyStep(h.policyEnforcer)
+		case "checkPolicy":
+			s, err = newCheckPolicyStep(h.policyChecker)
 		default:
 			if customStep, exists := steps[step]; exists {
 				s = customStep