help text and link for form labels #138 (#143)

* added help for timesheet duration form field - fixes #138
* added label option to link to manual chapter
* created docu chapter "timesheet" and added duration mode docu
* allow field and form option "documentation" to link to chapters in the documentation

src/Form/Extension/DocumentationLinkExtension.php

@@ -0,0 +1,49 @@
+<?php
+
+/*
+ * This file is part of the Kimai time-tracking app.
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace App\Form\Extension;
+
+use Symfony\Component\Form\AbstractTypeExtension;
+use Symfony\Component\Form\Extension\Core\Type\FormType;
+use Symfony\Component\Form\FormInterface;
+use Symfony\Component\Form\FormView;
+use Symfony\Component\OptionsResolver\OptionsResolver;
+
+/**
+ * Adds a linked help text with the link to the given documentation
+ */
+class DocumentationLinkExtension extends AbstractTypeExtension
+{
+    /**
+     * @return string
+     */
+    public function getExtendedType()
+    {
+        return FormType::class;
+    }
+
+    /**
+     * @param FormView $view
+     * @param FormInterface $form
+     * @param array $options
+     */
+    public function buildView(FormView $view, FormInterface $form, array $options)
+    {
+        $view->vars['documentation'] = $options['documentation'] ?? '';
+    }
+
+    /**
+     * @param OptionsResolver $resolver
+     */
+    public function configureOptions(OptionsResolver $resolver)
+    {
+        $resolver->setDefined(array('documentation'));
+        $resolver->setDefaults(['documentation' => null]);
+    }
+}