lib: Add HttpMethodNotAllowedException

At the moment we throw a Zend_Controller_Action_Exception when the HTTP method is not allowed.
I'll replace this w/ the exception introduced.

refs #6281

library/Icinga/Exception/Http/HttpMethodNotAllowedException.php

@@ -0,0 +1,41 @@
+<?php
+
+namespace Icinga\Exception\Http;
+
+use Icinga\Exception\IcingaException;
+
+/**
+ * Exception thrown if the HTTP method is not allowed
+ */
+class HttpMethodNotAllowedException extends IcingaException
+{
+    /**
+     * Allowed HTTP methods
+     *
+     * @var string
+     */
+    protected $allowedMethods;
+
+    /**
+     * Get the allowed HTTP methods
+     *
+     * @return string
+     */
+    public function getAllowedMethods()
+    {
+        return $this->allowedMethods;
+    }
+
+    /**
+     * Set the allowed HTTP methods
+     *
+     * @param   string $allowedMethods
+     *
+     * @return  $this
+     */
+    public function setAllowedMethods($allowedMethods)
+    {
+        $this->allowedMethods = (string) $allowedMethods;
+        return $this;
+    }
+}