made plugin compatible with Stud.IP 5.5 and PHP 8

controllers/file.php

@@ -114,7 +114,7 @@ class FileController extends PluginController
                 PageLayout::postError(
                     sprintf(
                         dgettext('NextcloudPlugin', 'Ein Fehler trat auf beim Aktualisieren der Datei „%s“.'),
-                        htmlReady($this->file_ref->name)
+                        htmlReady($this->file->getFilename())
                     ),
                     $this->errors
                 );
@@ -122,7 +122,7 @@ class FileController extends PluginController
                 PageLayout::postSuccess(
                     sprintf(
                         dgettext('NextcloudPlugin', 'Die Datei „%s“ wurde aktualisiert!'),
-                        htmlReady($this->file_ref->name)
+                        htmlReady($this->file->getFilename())
                     )
                 );
             }

plugin.manifest

 pluginname=NextcloudPlugin
 pluginclassname=NextcloudPlugin
-version=3.0.1
+version=3.1.0
 origin=data-quest
 studipMinVersion=5.0
-studipMaxVersion=5.4.99
+studipMaxVersion=5.5.99

views/file/edit.php

@@ -2,7 +2,7 @@
     <?= $aside_template->render() ?>
     <div id="file_management_forms">
         <form method="post" data-dialog class="default"
-              action="<?= $controller->link_for('/edit/' . $file->getId()) ?>">
+              action="<?= PluginEngine::getURL(NextcloudPlugin::class, [], 'file/edit/' . $file->getId()) ?>">
             <?= CSRFProtection::tokenTag() ?>
             <fieldset>
                 <legend><?= dgettext('NextcloudPlugin', 'Datei bearbeiten') ?></legend>

views/file/update.php

-<form action="<?= $controller->link_for('file/update/' . $file->getId(), ['from_plugin' => $from_plugin]) ?>"
+<form action="<?= PluginEngine::getURL(NextcloudPlugin::class, ['from_plugin' => $from_plugin], 'file/update/' . $file->getId()) ?>"
       enctype="multipart/form-data" method="post" class="default">
     <?= CSRFProtection::tokenTag() ?>
     <fieldset>