chore: import upstream snapshot with attribution

internal/auth/scope.go

@@ -0,0 +1,22 @@
+// Copyright (c) 2026 Lark Technologies Pte. Ltd.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import "strings"
+
+// MissingScopes returns the elements of required that are absent from storedScope.
+// storedScope is a space-separated list of granted scope strings (as stored in the token).
+func MissingScopes(storedScope string, required []string) []string {
+	granted := make(map[string]bool)
+	for _, s := range strings.Fields(storedScope) {
+		granted[s] = true
+	}
+	var missing []string
+	for _, s := range required {
+		if !granted[s] {
+			missing = append(missing, s)
+		}
+	}
+	return missing
+}