feat(client/v3/naming): add Attributes into Endpoint and deprecate Metadata

This implementation adds the new Attributes *attributes.Attributes into
Endpoint and deprecate Metadata accordingly. The metadata field is still
supported for backward compatibility

Signed-off-by: amosehiguese <[email protected]>

Author: amosehiguese

client/v3/naming/endpoints/endpoints.go

@@ -17,6 +17,8 @@ package endpoints
 import (
 	"context"
 
+	"google.golang.org/grpc/attributes"
+
 	clientv3 "go.etcd.io/etcd/client/v3"
 )
 
@@ -32,7 +34,14 @@ type Endpoint struct {
 	// Metadata is the information associated with Addr, which may be used
 	// to make load balancing decision.
 	// Since etcd 3.1
+	//
+	// Deprecated: use Attributes instead
 	Metadata any
+
+	// Attributes contains arbitrary data about this address intended for
+	// consumption by the SubConn.
+	// Since etcd 3.5
+	Attributes *attributes.Attributes
 }
 
 type Operation uint8

client/v3/naming/resolver/resolver.go

@@ -112,8 +112,9 @@ func convertToGRPCEndpoint(ups map[string]*endpoints.Update) []gresolver.Endpoin
 		ep := gresolver.Endpoint{
 			Addresses: []gresolver.Address{
 				{
-					Addr:     up.Endpoint.Addr,
-					Metadata: up.Endpoint.Metadata,
+					Addr:       up.Endpoint.Addr,
+					Metadata:   up.Endpoint.Metadata,
+					Attributes: up.Endpoint.Attributes,
 				},
 			},
 		}