feat: add support for S3 storage backend (#1080)

Co-authored-by: Alessandro (Ale) Segala <43508+ItalyPaleAle@users.noreply.github.com>

backend/internal/storage/filesystem_test.go

@@ -0,0 +1,68 @@
+package storage
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFilesystemStorageOperations(t *testing.T) {
+	ctx := context.Background()
+	store, err := NewFilesystemStorage(t.TempDir())
+	require.NoError(t, err)
+
+	t.Run("save, open and list files", func(t *testing.T) {
+		err := store.Save(ctx, "images/logo.png", bytes.NewBufferString("logo-data"))
+		require.NoError(t, err)
+
+		reader, size, err := store.Open(ctx, "images/logo.png")
+		require.NoError(t, err)
+		defer reader.Close()
+
+		contents, err := io.ReadAll(reader)
+		require.NoError(t, err)
+		assert.Equal(t, []byte("logo-data"), contents)
+		assert.Equal(t, int64(len(contents)), size)
+
+		err = store.Save(ctx, "images/nested/child.txt", bytes.NewBufferString("child"))
+		require.NoError(t, err)
+
+		files, err := store.List(ctx, "images")
+		require.NoError(t, err)
+		require.Len(t, files, 1)
+		assert.Equal(t, filepath.Join("images", "logo.png"), files[0].Path)
+		assert.Equal(t, int64(len("logo-data")), files[0].Size)
+	})
+
+	t.Run("delete files individually and idempotently", func(t *testing.T) {
+		err := store.Save(ctx, "images/delete-me.txt", bytes.NewBufferString("temp"))
+		require.NoError(t, err)
+
+		require.NoError(t, store.Delete(ctx, "images/delete-me.txt"))
+		_, _, err = store.Open(ctx, "images/delete-me.txt")
+		require.Error(t, err)
+		assert.True(t, IsNotExist(err))
+
+		// Deleting a missing object should be a no-op.
+		require.NoError(t, store.Delete(ctx, "images/missing.txt"))
+	})
+
+	t.Run("delete all files under a prefix", func(t *testing.T) {
+		require.NoError(t, store.Save(ctx, "images/a.txt", bytes.NewBufferString("a")))
+		require.NoError(t, store.Save(ctx, "images/b.txt", bytes.NewBufferString("b")))
+		require.NoError(t, store.DeleteAll(ctx, "images"))
+
+		_, _, err := store.Open(ctx, "images/a.txt")
+		require.Error(t, err)
+		assert.True(t, IsNotExist(err))
+
+		_, _, err = store.Open(ctx, "images/b.txt")
+		require.Error(t, err)
+		assert.True(t, IsNotExist(err))
+	})
+}