server: add error helper

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

server/errors_test.go

@@ -0,0 +1,19 @@
+package server
+
+import (
+	"testing"
+
+	"github.com/unistack-org/micro/v3/errors"
+)
+
+func TestError(t *testing.T) {
+	e := NewError("svc1")
+	err := e.BadRequest("%s", "test")
+	merr, ok := err.(*errors.Error)
+	if !ok {
+		t.Fatal("error not *errors.Error")
+	}
+	if merr.Id != "svc1" {
+		t.Fatal("id != svc1")
+	}
+}