Add docs for the ConfigFormEventsHook

doc/60-Hooks.md

@@ -0,0 +1,49 @@
+# Hooks
+
+## ConfigFormEventsHook
+
+The `ConfigFormEventsHook` allows developers to hook into the handling of configuration forms. It provides three methods:
+
+* `appliesTo()`
+* `isValid()`
+* `onSuccess()`
+
+`appliesTo()` determines whether the hook should run for a given configuration form.
+Developers should use `instanceof` checks in order to decide whether the hook should run or not.
+If `appliesTo()` returns `false`, `isValid()` and `onSuccess()` won't get called for this hook.
+
+`isValid()` is called after the configuration form has been validated successfully.
+An exception thrown here indicates form errors and prevents the config from being stored.
+The exception's error message is shown in the frontend automatically.
+If there are multiple hooks indicating errors, every error will be displayed.
+
+`onSuccess()` is called after the configuration has been stored successfully.
+Form handling can't be interrupted here. Any exception will be caught, logged and notified.
+
+Hook example:
+
+```php
+namespace Icinga\Module\Acme\ProvidedHook;
+
+use Icinga\Application\Hook\ConfigFormEventsHook;
+use Icinga\Forms\ConfigForm;
+use Icinga\Forms\Security\RoleForm;
+
+class ConfigFormEvents extends ConfigFormEventsHook
+{
+    public function appliesTo(ConfigForm $form)
+    {
+        return $form instanceof RoleForm;
+    }
+
+    public function onSuccess(ConfigForm $form)
+    {
+        $this->updateMyModuleConfig();
+    }
+
+    protected function updateMyModuleConfig()
+    {
+        // ...
+    }
+}
+```