Fix various compatibility issues with PHP 8

libs/swiftmailer/classes/Swift/Encoder.php

@@ -0,0 +1,28 @@
+<?php
+
+/*
+ * This file is part of SwiftMailer.
+ * (c) 2004-2009 Chris Corbyn
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+/**
+ * Interface for all Encoder schemes.
+ *
+ * @author Chris Corbyn
+ */
+interface Swift_Encoder extends Swift_Mime_CharsetObserver
+{
+    /**
+     * Encode a given string to produce an encoded string.
+     *
+     * @param string $string
+     * @param int    $firstLineOffset if first line needs to be shorter
+     * @param int    $maxLineLength   - 0 indicates the default length for this encoding
+     *
+     * @return string
+     */
+    public function encodeString($string, $firstLineOffset = 0, $maxLineLength = 0);
+}