feat(message-gateway): add channel types, registry, and pairing codes

pkg/message_gateway/pairing.go

@@ -0,0 +1,50 @@
+// Copyright 2026 Arctel.net
+// SPDX-License-Identifier: Apache-2.0
+
+package message_gateway
+
+import (
+	"crypto/rand"
+	"strings"
+	"unicode"
+)
+
+// CodeAlphabet excludes easily confused runes 0/O/1/I.
+const CodeAlphabet = "ABCDEFGHJKLMNPQRSTUVWXYZ23456789"
+
+// CodeLength is the raw pairing code size.
+const CodeLength = 8
+
+// GenerateCode returns an 8-character pairing code.
+func GenerateCode() (string, error) {
+	buf := make([]byte, CodeLength)
+	if _, err := rand.Read(buf); err != nil {
+		return "", err
+	}
+	out := make([]byte, CodeLength)
+	for i, b := range buf {
+		out[i] = CodeAlphabet[int(b)%len(CodeAlphabet)]
+	}
+	return string(out), nil
+}
+
+// NormalizeCode strips separators and uppercases.
+func NormalizeCode(s string) string {
+	var b strings.Builder
+	for _, r := range s {
+		if r == '-' || unicode.IsSpace(r) {
+			continue
+		}
+		b.WriteRune(unicode.ToUpper(r))
+	}
+	return b.String()
+}
+
+// FormatCode renders ABCD-EFGH.
+func FormatCode(s string) string {
+	s = NormalizeCode(s)
+	if len(s) != CodeLength {
+		return s
+	}
+	return s[:4] + "-" + s[4:]
+}