Added POST then PUT method

$ helm push --username mstore --password mstore --insecure-skip-tls-verify DIST/mstore-0.2.0.tgz oci://localhost:1025/mstore
Pushed: localhost:1025/mstore/mstore:0.2.0
Digest: sha256:5a60793c9fc655e1940b00dac707632d7d3b32aad31a79acc41e65f9152e50fc

app/operator/blob.go

@@ -217,9 +217,19 @@ func (oper *Operator) PutUpload(ctx context.Context, operatorID string, params *
 
 	}
 	if contentLength != 0 {
-		// TODO
-		err = fmt.Errorf("Unexpected Content-Length header: %s", params.ContentLength)
-		return res, http.StatusInternalServerError, err
+		recsize, _, err := oper.store.WriteUpload(params.Reference, params.Reader)
+		if err != nil {
+			return res, http.StatusInternalServerError, err
+		}
+		if contentLength != 0 && recsize != contentLength {
+			oper.store.RemoveUpload(params.Reference)
+			err = fmt.Errorf("Mismatch upload recorded size and content length")
+			return res, http.StatusInternalServerError, err
+		}
+		if err != nil {
+			return res, http.StatusInternalServerError, err
+		}
+		res.Location = fmt.Sprintf("/v2/%s/blobs/%s", params.Name, params.Digest)
 	}
 
 	err = oper.store.LinkUpload(params.Reference, params.Digest)