Add base form class for configuration forms

refs #5525

application/forms/ConfigForm.php

@@ -0,0 +1,67 @@
+<?php
+// {{{ICINGA_LICENSE_HEADER}}}
+// {{{ICINGA_LICENSE_HEADER}}}
+
+namespace Icinga\Form;
+
+use Exception;
+use Icinga\Web\Form;
+use Icinga\Application\Config;
+use Icinga\Config\PreservingIniWriter;
+
+/**
+ * Form base-class providing standard functionality for configuration forms
+ */
+class ConfigForm extends Form
+{
+    /**
+     * The configuration to work with
+     *
+     * @var Config
+     */
+    protected $config;
+
+    /**
+     * Set the configuration to use when populating the form or when saving the user's input
+     *
+     * @param   Config      $config     The configuration to use
+     *
+     * @return  self
+     */
+    public function setConfig(Config $config)
+    {
+        $this->config = $config;
+        return $this;
+    }
+
+    /**
+     * Persist the current configuration to disk
+     *
+     * If an error occurs the user is shown a view describing the issue and displaying the raw INI configuration.
+     *
+     * @return  bool                    Whether the configuration could be persisted
+     */
+    public function save()
+    {
+        $writer = new PreservingIniWriter(
+            array(
+                'config'    => $this->config,
+                'filename'  => $this->config->getConfigFile()
+            )
+        );
+
+        try {
+            $writer->write();
+        } catch (Exception $e) {
+            $this->addDecorator('ViewScript', array(
+                'viewScript'    => 'showConfiguration.phtml',
+                'errorMessage'  => $e->getMessage(),
+                'configString'  => $writer->render(),
+                'filePath'      => $this->config->getConfigFile()
+            ));
+            return false;
+        }
+
+        return true;
+    }
+}

application/views/scripts/showConfiguration.phtml

@@ -0,0 +1,28 @@
+<div>
+  <h4><?= $this->translate('Saving Configuration Failed'); ?></h4>
+  <br>
+  <p>
+    <?= sprintf(
+      $this->translate('The file %s couldn\'t be stored. (Error: "%s")'),
+      $this->escape($filePath),
+      $this->escape($errorMessage)
+    ); ?>
+    <br>
+    <?= $this->translate('This could have one or more of the following reasons:'); ?>
+  </p>
+  <ul>
+    <li><?= $this->translate('You don\'t have file-system permissions to write to the file'); ?></li>
+    <li><?= $this->translate('Something went wrong while writing the file'); ?></li>
+    <li><?= $this->translate('There\'s an application error preventing you from persisting the configuration'); ?></li>
+  </ul>
+</div>
+<p>
+  <?= $this->translate('Details can be found in the application log. (If you don\'t have access to this log, call your administrator in this case)'); ?>
+  <br>
+  <?= $this->translate('In case you can access the file by yourself, you can open it and insert the config manually:'); ?>
+</p>
+<p>
+  <pre>
+    <code><?= $this->escape($configString); ?></code>
+  </pre>
+</p>