async redirects() {
    return [
      {
        // this will match `/english(default)/something` being requested
        source: '/english\\(default\\)/:slug',
        destination: '/en-us/:slug',
        permanent: false,
      },
    ]
  },
}
Header, Cookie, and Query Matching
To only match a redirect when header, cookie, or query values also match the has field or don't match the missing field can be used. Both the source and all has items must match and all missing items must not match for the redirect to be applied.
has and missing items can have the following fields:
type: String - must be either header, cookie, host, or query.
key: String - the key from the selected type to match against.