feat: Add white list support to Casbin middleware

• Introduced a new WithWhiteList option to allow bypassing Casbin checks for specified API routes.
• Modified Server middleware to check if the current request path is in the white list before performing Casbin authorization.
• Updated options struct to include a whiteList field, which holds a map of paths to be excluded from Casbin enforcement.
• Refactored the Server function to skip Casbin checks for white-listed routes, improving flexibility for open or less restricted endpoints.