fix(bzz): add omitempty to redundancy level validation in download and serveReference

Author: akrem-chabchoub

pkg/api/bzz.go

@@ -387,7 +387,7 @@ func (s *Service) serveReference(logger log.Logger, address swarm.Address, pathV
 		Cache                 *bool             `map:"Swarm-Cache"`
 		Strategy              *getter.Strategy  `map:"Swarm-Redundancy-Strategy"`
 		FallbackMode          *bool             `map:"Swarm-Redundancy-Fallback-Mode"`
-		RLevel                *redundancy.Level `map:"Swarm-Redundancy-Level" validate:"lte=4"`
+		RLevel                *redundancy.Level `map:"Swarm-Redundancy-Level" validate:"omitempty,lte=4"`
 		ChunkRetrievalTimeout *string           `map:"Swarm-Chunk-Retrieval-Timeout"`
 	}{}
 
@@ -599,7 +599,7 @@ func (s *Service) serveManifestEntry(
 func (s *Service) downloadHandler(logger log.Logger, w http.ResponseWriter, r *http.Request, reference swarm.Address, additionalHeaders http.Header, etag, headersOnly bool, rootCh swarm.Chunk) {
 	headers := struct {
 		Strategy              *getter.Strategy  `map:"Swarm-Redundancy-Strategy"`
-		RLevel                *redundancy.Level `map:"Swarm-Redundancy-Level" validate:"lte=4"`
+		RLevel                *redundancy.Level `map:"Swarm-Redundancy-Level" validate:"omitempty,lte=4"`
 		FallbackMode          *bool             `map:"Swarm-Redundancy-Fallback-Mode"`
 		ChunkRetrievalTimeout *string           `map:"Swarm-Chunk-Retrieval-Timeout"`
 		LookaheadBufferSize   *int              `map:"Swarm-Lookahead-Buffer-Size"`