doc: mark CustomCodec as deprecated (#3698)

server.go

@@ -243,6 +243,12 @@ func KeepaliveEnforcementPolicy(kep keepalive.EnforcementPolicy) ServerOption {
 // CustomCodec returns a ServerOption that sets a codec for message marshaling and unmarshaling.
 //
 // This will override any lookups by content-subtype for Codecs registered with RegisterCodec.
+//
+// Deprecated: register codecs using encoding.RegisterCodec. The server will
+// automatically use registered codecs based on the incoming requests' headers.
+// See also
+// https://github.com/grpc/grpc-go/blob/master/Documentation/encoding.md#using-a-codec.
+// Will be supported throughout 1.x.
 func CustomCodec(codec Codec) ServerOption {
 	return newFuncServerOption(func(o *serverOptions) {
 		o.codec = codec
@@ -255,7 +261,8 @@ func CustomCodec(codec Codec) ServerOption {
 // default, server messages will be sent using the same compressor with which
 // request messages were sent.
 //
-// Deprecated: use encoding.RegisterCompressor instead.
+// Deprecated: use encoding.RegisterCompressor instead. Will be supported
+// throughout 1.x.
 func RPCCompressor(cp Compressor) ServerOption {
 	return newFuncServerOption(func(o *serverOptions) {
 		o.cp = cp
@@ -266,7 +273,8 @@ func RPCCompressor(cp Compressor) ServerOption {
 // messages.  It has higher priority than decompressors registered via
 // encoding.RegisterCompressor.
 //
-// Deprecated: use encoding.RegisterCompressor instead.
+// Deprecated: use encoding.RegisterCompressor instead. Will be supported
+// throughout 1.x.
 func RPCDecompressor(dc Decompressor) ServerOption {
 	return newFuncServerOption(func(o *serverOptions) {
 		o.dc = dc
@@ -276,7 +284,7 @@ func RPCDecompressor(dc Decompressor) ServerOption {
 // MaxMsgSize returns a ServerOption to set the max message size in bytes the server can receive.
 // If this is not set, gRPC uses the default limit.
 //
-// Deprecated: use MaxRecvMsgSize instead.
+// Deprecated: use MaxRecvMsgSize instead. Will be supported throughout 1.x.
 func MaxMsgSize(m int) ServerOption {
 	return MaxRecvMsgSize(m)
 }

vet.sh

@@ -135,6 +135,7 @@ balancer.Picker
 grpc.CallCustomCodec
 grpc.Code
 grpc.Compressor
+grpc.CustomCodec
 grpc.Decompressor
 grpc.MaxMsgSize
 grpc.MethodConfig