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

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

backend/internal/storage/storage.go

@@ -0,0 +1,33 @@
+package storage
+
+import (
+	"context"
+	"io"
+	"os"
+	"time"
+)
+
+var (
+	TypeFileSystem = "fs"
+	TypeS3         = "s3"
+)
+
+type ObjectInfo struct {
+	Path    string
+	Size    int64
+	ModTime time.Time
+}
+
+type FileStorage interface {
+	Save(ctx context.Context, relativePath string, data io.Reader) error
+	Open(ctx context.Context, relativePath string) (io.ReadCloser, int64, error)
+	Delete(ctx context.Context, relativePath string) error
+	DeleteAll(ctx context.Context, prefix string) error
+	List(ctx context.Context, prefix string) ([]ObjectInfo, error)
+	Walk(ctx context.Context, root string, fn func(ObjectInfo) error) error
+	Type() string
+}
+
+func IsNotExist(err error) bool {
+	return os.IsNotExist(err)
+}