Add configuration option to use null message handler

Author: tepeds

config/sns-handler.php

@@ -1,5 +1,6 @@
 <?php
 
 return [
+    'validate-sns-messages' => env('VALIDATE_SNS_MESSAGES', true),
     'sns-class-map' => []
 ];

src/ServiceProvider.php

@@ -3,6 +3,7 @@
 
 namespace MiamiOH\SnsHandler;
 
+use Aws\Sns\MessageValidator;
 use Illuminate\Support\ServiceProvider as BaseServiceProvider;
 use MiamiOH\SnsHandler\Controllers\SnsMessageController;
 
@@ -32,7 +33,13 @@ public function boot()
     public function register()
     {
         $this->app->make(SnsMessageController::class);
+
         $this->mergeConfigFrom($this->configPath, 'sns-handler');
+
+        if (!config('validate-sns-messages')) {
+            $this->app->bind(MessageValidator::class, NullMessageValidator::class);
+        }
+
         $this->app->bind(SnsTopicMapper::class, function () {
             return new SnsTopicMapper(config('sns-handler.sns-class-map', []));
         });