Add grpc plugin (#2758)

* Add grpc plugin

* remove stale readmes

client/grpc/error.go

@@ -0,0 +1,69 @@
+package grpc
+
+import (
+	"net/http"
+
+	"go-micro.dev/v5/errors"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+func microError(err error) error {
+	// no error
+	switch err {
+	case nil:
+		return nil
+	}
+
+	if verr, ok := err.(*errors.Error); ok {
+		return verr
+	}
+
+	// grpc error
+	s, ok := status.FromError(err)
+	if !ok {
+		return err
+	}
+
+	// return first error from details
+	if details := s.Details(); len(details) > 0 {
+		return microError(details[0].(error))
+	}
+
+	// try to decode micro *errors.Error
+	if e := errors.Parse(s.Message()); e.Code > 0 {
+		return e // actually a micro error
+	}
+
+	// fallback
+	return errors.New("go.micro.client", s.Message(), microStatusFromGrpcCode(s.Code()))
+}
+
+func microStatusFromGrpcCode(code codes.Code) int32 {
+	switch code {
+	case codes.OK:
+		return http.StatusOK
+	case codes.InvalidArgument:
+		return http.StatusBadRequest
+	case codes.DeadlineExceeded:
+		return http.StatusRequestTimeout
+	case codes.NotFound:
+		return http.StatusNotFound
+	case codes.AlreadyExists:
+		return http.StatusConflict
+	case codes.PermissionDenied:
+		return http.StatusForbidden
+	case codes.Unauthenticated:
+		return http.StatusUnauthorized
+	case codes.FailedPrecondition:
+		return http.StatusPreconditionFailed
+	case codes.Unimplemented:
+		return http.StatusNotImplemented
+	case codes.Internal:
+		return http.StatusInternalServerError
+	case codes.Unavailable:
+		return http.StatusServiceUnavailable
+	}
+
+	return http.StatusInternalServerError
+}