Use generator to generate exceptions from yaml

Signed-off-by: Asai Neko <sugar@sne.moe>

internal/exception/status_gen.go

@@ -0,0 +1,9 @@
+// Code generated by gen-exception; DO NOT EDIT.
+package exception
+
+const (
+	StatusClient = "6"
+	StatusSuccess = "2"
+	StatusUser = "4"
+	StatusServer = "5"
+)