Add getModule() to HookEssentials

Ported from `Hook\Common\HookUtils` in Icinga DB Web, generalized to return
null when the hook is not registered under a module namespace.

Author: lippserd

library/Icinga/Application/Hook/HookEssentials.php

@@ -5,7 +5,10 @@
 
 namespace Icinga\Application\Hook;
 
+use Icinga\Application\ClassLoader;
 use Icinga\Application\Hook;
+use Icinga\Application\Icinga;
+use Icinga\Application\Modules\Module;
 
 /**
  * Provides the mechanism for hook registration and retrieval
@@ -49,6 +52,24 @@ public static function first(): ?static
         return Hook::first(static::getHookName());
     }
 
+    /**
+     * Get the module this hook belongs to, if any
+     *
+     * Returns null when the hook class is not part of a module namespace.
+     *
+     * @return ?Module
+     */
+    public function getModule(): ?Module
+    {
+        if (! ClassLoader::classBelongsToModule(static::class)) {
+            return null;
+        }
+
+        $moduleName = ClassLoader::extractModuleName(static::class);
+
+        return Icinga::app()->getModuleManager()->getModule($moduleName);
+    }
+
     /**
      * Register the hook
      *