feat: add database storage backend (#1091)

Co-authored-by: Elias Schneider <login@eliasschneider.com>

backend/internal/utils/stream_util.go

@@ -0,0 +1,34 @@
+package utils
+
+import (
+	"errors"
+	"io"
+)
+
+var ErrSizeExceeded = errors.New("stream size exceeded")
+
+// LimitReader is like io.LimitReader but throws an error if the stream exceeds the max size
+// io.LimitReader instead just returns io.EOF
+// Adapted from https://github.com/golang/go/issues/51115#issuecomment-1079761212
+type LimitReader struct {
+	io.ReadCloser
+	N int64
+}
+
+func NewLimitReader(r io.ReadCloser, limit int64) *LimitReader {
+	return &LimitReader{r, limit}
+}
+
+func (r *LimitReader) Read(p []byte) (n int, err error) {
+	if r.N <= 0 {
+		return 0, ErrSizeExceeded
+	}
+
+	if int64(len(p)) > r.N {
+		p = p[0:r.N]
+	}
+
+	n, err = r.ReadCloser.Read(p)
+	r.N -= int64(n)
+	return
+}