Adjust arbitrary keys to custom claims field to prevent conflicts

src/server/auth/types.ts

@@ -23,7 +23,9 @@ export interface AuthInfo {
   expiresAt?: number;
 
   /**
-   * Additional arbitrary properties that may be included.
+   * Additional custom claims associated with the token.
+   * This field should be used for any additional data that needs to be attached to the auth info.
+   * Using this field instead of arbitrary keys ensures compatibility with future interface changes.
    */
-  [key: string]: unknown;
+  customClaims?: Record<string, unknown>;
 }