Import latest app updates from streamline

An updated set of source files and initialization was provided by streamline to
address issues observed during initial testing. These files have been updated in
order to generate a new set of app images.

docker/streamline-src/vendor/symfony/mime/Part/AbstractPart.php

@@ -1,65 +0,0 @@
-<?php
-
-/*
- * This file is part of the Symfony package.
- *
- * (c) Fabien Potencier <fabien@symfony.com>
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Symfony\Component\Mime\Part;
-
-use Symfony\Component\Mime\Header\Headers;
-
-/**
- * @author Fabien Potencier <fabien@symfony.com>
- */
-abstract class AbstractPart
-{
-    private Headers $headers;
-
-    public function __construct()
-    {
-        $this->headers = new Headers();
-    }
-
-    public function getHeaders(): Headers
-    {
-        return $this->headers;
-    }
-
-    public function getPreparedHeaders(): Headers
-    {
-        $headers = clone $this->headers;
-        $headers->setHeaderBody('Parameterized', 'Content-Type', $this->getMediaType().'/'.$this->getMediaSubtype());
-
-        return $headers;
-    }
-
-    public function toString(): string
-    {
-        return $this->getPreparedHeaders()->toString()."\r\n".$this->bodyToString();
-    }
-
-    public function toIterable(): iterable
-    {
-        yield $this->getPreparedHeaders()->toString();
-        yield "\r\n";
-        yield from $this->bodyToIterable();
-    }
-
-    public function asDebugString(): string
-    {
-        return $this->getMediaType().'/'.$this->getMediaSubtype();
-    }
-
-    abstract public function bodyToString(): string;
-
-    abstract public function bodyToIterable(): iterable;
-
-    abstract public function getMediaType(): string;
-
-    abstract public function getMediaSubtype(): string;
-}