feat(message-gateway): add user bind and unbind APIs

internal/apps/message_gateway/errs.go

@@ -0,0 +1,16 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package message_gateway
+
+import "errors"
+
+var (
+	errCodeInvalid          = errors.New("invalid or expired pairing code")
+	errChannelMismatch      = errors.New("pairing code does not match channel")
+	errPlatformAlreadyBound = errors.New("this platform account is already bound")
+	errBindingNotFound      = errors.New("binding not found")
+	errBindingForbidden     = errors.New("cannot unbind another user's binding")
+	errChannelIDRequired    = errors.New("channel_id is required")
+	errChannelDisabled      = errors.New("channel is not enabled")
+)