Cannot generate function for API's that use Servant.Auth

[Sakuya-Izayoi]

I have an endpoint that looks approximately like this:

SAS.Auth [SAS.Cookie] LoggedIn :> Capture "tournamentId" TournamentId :> "start" :> Post '[JSON] (Entity Tournament)

Unfortunately, attempt to generate JS for this API does not typecheck. The error is:

app\Main.hs:24:14: error:
    * No instance for (servant-foreign-0.15.4:Servant.Foreign.Internal.HasForeign
                         NoTypes NoContent StartTournamentApi)
        arising from a use of `jsForAPI'
    * In the expression:
        jsForAPI (Proxy :: Proxy StartTournamentApi) jquery
      In an equation for `js':
          js = jsForAPI (Proxy :: Proxy StartTournamentApi) jquery
      In the expression:
        do let js = jsForAPI (Proxy :: Proxy StartTournamentApi) jquery
           TIO.writeFile "static/js/api.js" js
   |
24 |     let js = jsForAPI (Proxy :: Proxy StartTournamentApi) jquery

I assume that js generator should completely ignore auth requirement because XMLHttpRequest sends cookies which are used for authentication.

The workaround I found is to create a following instance:

instance HasForeign lang ftype api => HasForeign lang ftype (Auth auths val :> api) where
    type Foreign ftype (Auth auths val :> api) = Foreign ftype api
    foreignFor lang ftype Proxy = foreignFor lang ftype (Proxy :: Proxy api)