Build modified streamline images

The official image from streamline does not currently work for the arm64
platform. As a temporary measure, the source code and docker build scripts
have been lifted from the official images and are used to build locally.

Some additional modifications are made to reduce overall image size, these
are documented in docker/README.md

docker/streamline-src/vendor/league/flysystem/src/UnableToGeneratePublicUrl.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\Flysystem;
+
+use RuntimeException;
+use Throwable;
+
+final class UnableToGeneratePublicUrl extends RuntimeException implements FilesystemException
+{
+    public function __construct(string $reason, string $path, ?Throwable $previous = null)
+    {
+        parent::__construct("Unable to generate public url for $path: $reason", 0, $previous);
+    }
+
+    public static function dueToError(string $path, Throwable $exception): static
+    {
+        return new static($exception->getMessage(), $path, $exception);
+    }
+
+    public static function noGeneratorConfigured(string $path, string $extraReason = ''): static
+    {
+        return new static('No generator was configured ' . $extraReason, $path);
+    }
+}