Handle config decoding errors from DB charset issues (#333)

If the database's character set is not set correctly, the decoding of
the config attributes may fail. For that case an error message will be
rendered in the form. There will also be a docs entry to prevent that.

Closes #271

Author: nilmerg

application/forms/ChannelForm.php

@@ -6,14 +6,16 @@
 
 use DateTime;
 use Icinga\Exception\Http\HttpNotFoundException;
-use Icinga\Module\Notifications\Model\Channel;
 use Icinga\Module\Notifications\Model\AvailableChannelType;
+use Icinga\Module\Notifications\Model\Channel;
 use Icinga\Module\Notifications\Model\Contact;
 use Icinga\Module\Notifications\Model\RuleEscalationRecipient;
 use Icinga\Web\Session;
+use ipl\Html\Attributes;
 use ipl\Html\Contract\FormSubmitElement;
 use ipl\Html\FormElement\BaseFormElement;
 use ipl\Html\FormElement\FieldsetElement;
+use ipl\Html\HtmlElement;
 use ipl\I18n\GettextTranslator;
 use ipl\I18n\StaticTranslator;
 use ipl\Sql\Connection;
@@ -267,6 +269,24 @@ protected function createConfigElements(string $type, string $config): void
         $elementsConfig = json_decode($config, true);
 
         if (empty($elementsConfig)) {
+            $this->prependHtml(
+                HtmlElement::create(
+                    'ul',
+                    Attributes::create(['class' => 'errors']),
+                    HtmlElement::create(
+                        'li',
+                        null,
+                        sprintf(
+                            $this->translate(
+                                'Could not decode options for type \'%s\'.'
+                                . ' Check if your database\'s character set is correctly configured.'
+                            ),
+                            $type
+                        )
+                    )
+                )
+            );
+
             return;
         }
 
@@ -449,4 +469,20 @@ private function fetchDbValues(): array
             'config'    => json_decode($channel->config, true) ?? []
         ];
     }
+
+    /**
+     * Validate all elements
+     *
+     * @return $this
+     */
+    public function validate(): self
+    {
+        parent::validate();
+
+        if (! $this->hasElement('config')) {
+            $this->isValid = false;
+        }
+
+        return $this;
+    }
 }

library/Notifications/Common/Database.php

@@ -82,6 +82,13 @@ private static function getConnection(): Connection
                 . ",NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION'";
         }
 
+        if (empty($config->charset)) {
+            $config->charset = match ($config->db) {
+                'mysql' => 'utf8mb4',
+                default => 'utf8',
+            };
+        }
+
         $db = new Connection($config);
 
         $adapter = $db->getAdapter();