grpc client/server fixes (#1355)

* grpc client/server fixes

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

errors/errors.go

@@ -115,3 +115,22 @@ func InternalServerError(id, format string, a ...interface{}) error {
 		Status: http.StatusText(500),
 	}
 }
+
+func Equal(err1 error, err2 error) bool {
+	verr1, ok1 := err1.(*Error)
+	verr2, ok2 := err2.(*Error)
+
+	if ok1 != ok2 {
+		return false
+	}
+
+	if !ok1 {
+		return err1 == err2
+	}
+
+	if verr1.Code != verr2.Code {
+		return false
+	}
+
+	return true
+}