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/UnableToMountFilesystem.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace League\Flysystem;
+
+use LogicException;
+
+class UnableToMountFilesystem extends LogicException implements FilesystemException
+{
+    /**
+     * @param mixed $key
+     */
+    public static function becauseTheKeyIsNotValid($key): UnableToMountFilesystem
+    {
+        return new UnableToMountFilesystem(
+            'Unable to mount filesystem, key was invalid. String expected, received: ' . gettype($key)
+        );
+    }
+
+    /**
+     * @param mixed $filesystem
+     */
+    public static function becauseTheFilesystemWasNotValid($filesystem): UnableToMountFilesystem
+    {
+        $received = is_object($filesystem) ? get_class($filesystem) : gettype($filesystem);
+
+        return new UnableToMountFilesystem(
+            'Unable to mount filesystem, filesystem was invalid. Instance of ' . FilesystemOperator::class . ' expected, received: ' . $received
+        );
+    }
+}