initial commit: WIP debugging PAM module

rust-backend/src/error.rs

@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: Apache-2.0
+// Copyright 2026 Suyono
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
+
+pub const SUCCESS: i32 = 0;
+pub const ERR_INVALID_INPUT: i32 = -1;
+pub const ERR_AUTH_FAILED: i32 = -2;
+pub const ERR_PANIC: i32 = -99;