test(05-04): add failing tests for attach File, Thumb, and bucket

- ThumbFilename/PartitionDirectory/File.Thumb behavior tests
- OpenBucket fail-loud and memblob tests
- Migrate empty plugin list must create system_files

lagoon/attach/thumb.go

@@ -0,0 +1,25 @@
+package attach
+
+import (
+	"context"
+	"fmt"
+	"image"
+
+	"gocloud.dev/blob"
+)
+
+func ThumbFilename(id uint, w, h int, offsetX, offsetY int, mode, ext string) string {
+	return ""
+}
+
+func PartitionDirectory(diskName string) string {
+	return ""
+}
+
+func (f *File) Thumb(ctx context.Context, bucket *blob.Bucket, w, h int, mode string) (string, error) {
+	return "", fmt.Errorf("attach: thumb not implemented")
+}
+
+var resizeImage = func(src image.Image, w, h int, mode string) image.Image {
+	return src
+}