Generic sort options in persistent

Model.hs

{-# LANGUAGE QuasiQuotes, TemplateHaskell, TypeFamilies #-}
{-# LANGUAGE OverloadedStrings, GADTs #-}

import Data.Text (Text)
import Data.Time (UTCTime)
import Database.Persist
import Database.Persist.Sqlite (runSqlite, runMigration)
import Database.Persist.TH (mkPersist, persistLowerCase, sqlSettings)

mkPersist sqlSettings [persistLowerCase|
Model
   name     Text
   created  UTCTime
   deriving Show
|]

getModelSorterOpt :: Text -> Text -> Maybe (SelectOpt Model)
getModelSorterOpt sortOrder sortField = 
    case sortField of
        "id" -> Just   $ sortOrder' ModelId
        "name" -> Just $ sortOrder' ModelName
        "created" -> Just $ sortOrder' ModelCreated
        _ -> Nothing
    where sortOrder' :: EntityField Model typ -> SelectOpt Model
          sortOrder' = case sortOrder of 
            "Asc" -> Asc
            "Desc" -> Desc