Remote codec-endpoint cherry-pick

[dandavison]

Cherry-pick of #384 with vendoring of sdk-go code.

[cretz]

Just a small note on some code that can be removed, but otherwise LGTM

[cretz]

Suggested change

	type remoteDataConverter struct {
	parent converter.DataConverter
	payloadCodec converter.PayloadCodec
	}
	// NewRemoteDataConverter wraps the given parent DataConverter and performs
	// encoding/decoding on the payload via the remote endpoint.
	func NewRemoteDataConverter(parent converter.DataConverter, options converter.RemoteDataConverterOptions) converter.DataConverter {
	options.Endpoint = strings.TrimSuffix(options.Endpoint, "/")
	payloadCodec := NewRemotePayloadCodec(RemotePayloadCodecOptions(options))
	return &remoteDataConverter{parent, payloadCodec}
	}
	// ToPayload implements DataConverter.ToPayload performing remote encoding on the
	// result of the parent's ToPayload call.
	func (rdc *remoteDataConverter) ToPayload(value interface{}) (*commonpb.Payload, error) {
	payload, err := rdc.parent.ToPayload(value)
	if payload == nil || err != nil {
	return payload, err
	}
	encodedPayloads, err := rdc.payloadCodec.Encode([]*commonpb.Payload{payload})
	if err != nil {
	return payload, err
	}
	return encodedPayloads[0], err
	}
	// ToPayloads implements DataConverter.ToPayloads performing remote encoding on the
	// result of the parent's ToPayloads call.
	func (rdc *remoteDataConverter) ToPayloads(value ...interface{}) (*commonpb.Payloads, error) {
	payloads, err := rdc.parent.ToPayloads(value...)
	if payloads == nil || err != nil {
	return payloads, err
	}
	encodedPayloads, err := rdc.payloadCodec.Encode(payloads.Payloads)
	return &commonpb.Payloads{Payloads: encodedPayloads}, err
	}
	// FromPayload implements DataConverter.FromPayload performing remote decoding on the
	// given payload before sending to the parent FromPayload.
	func (rdc *remoteDataConverter) FromPayload(payload *commonpb.Payload, valuePtr interface{}) error {
	decodedPayloads, err := rdc.payloadCodec.Decode([]*commonpb.Payload{payload})
	if err != nil {
	return err
	}
	return rdc.parent.FromPayload(decodedPayloads[0], valuePtr)
	}
	// FromPayloads implements DataConverter.FromPayloads performing remote decoding on the
	// given payloads before sending to the parent FromPayloads.
	func (rdc *remoteDataConverter) FromPayloads(payloads *commonpb.Payloads, valuePtrs ...interface{}) error {
	if payloads == nil {
	return rdc.parent.FromPayloads(payloads, valuePtrs...)
	}
	decodedPayloads, err := rdc.payloadCodec.Decode(payloads.Payloads)
	if err != nil {
	return err
	}
	return rdc.parent.FromPayloads(&commonpb.Payloads{Payloads: decodedPayloads}, valuePtrs...)
	}
	// ToString implements DataConverter.ToString performing remote decoding on the given
	// payload before sending to the parent ToString.
	func (rdc *remoteDataConverter) ToString(payload *commonpb.Payload) string {
	if payload == nil {
	return rdc.parent.ToString(payload)
	}
	decodedPayloads, err := rdc.payloadCodec.Decode([]*commonpb.Payload{payload})
	if err != nil {
	return err.Error()
	}
	return rdc.parent.ToString(decodedPayloads[0])
	}
	// ToStrings implements DataConverter.ToStrings using ToString for each value.
	func (rdc *remoteDataConverter) ToStrings(payloads *commonpb.Payloads) []string {
	if payloads == nil {
	return nil
	}
	strs := make([]string, len(payloads.Payloads))
	// Perform decoding one by one here so that we return individual errors
	for i, payload := range payloads.Payloads {
	strs[i] = rdc.ToString(payload)
	}
	return strs
	}

I think you can remove all of this

[dandavison]

Thanks, that's right.