I am working with Persist data constructors, and I would like to be able to derive generic (on the second file) just like it is done on the first file

internet_example.hs

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-- from http://seanhess.github.io/2015/08/19/practical-haskell-json-api.html
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{-# LANGUAGE DeriveGeneric #-}

module Main where

import Data.Monoid ((<>))
import Data.Aeson (FromJSON, ToJSON)
import GHC.Generics
import Web.Scotty

data User = User { userId :: Int, userName :: String } deriving (Show, Generic)
instance ToJSON User
instance FromJSON User

myfile.hs

{-# LANGUAGE EmptyDataDecls             #-}
{-# LANGUAGE FlexibleContexts           #-}
{-# LANGUAGE GADTs                      #-}
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
{-# LANGUAGE MultiParamTypeClasses      #-}
{-# LANGUAGE OverloadedStrings          #-}
{-# LANGUAGE QuasiQuotes                #-}
{-# LANGUAGE TemplateHaskell            #-}
{-# LANGUAGE TypeFamilies               #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-}

module Model where

import Control.Monad.IO.Class  (liftIO)
import Control.Monad.Logger    (runStderrLoggingT, NoLoggingT)
import Control.Monad.Trans.Reader (ReaderT)
import Control.Monad.Trans.Resource (ResourceT)
import Database.Persist
import Database.Persist.Postgresql
import Database.Persist.TH
import Data.Time
import Data.Int
import GHC.Generics
import Data.Aeson (FromJSON, ToJSON)


share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistLowerCase|
Users
    email String
    password String
    alias String
    image_url String
    show_email Bool
    UniqueEmail email
    date UTCTime default=CURRENT_TIMESTAMP
    deriving (Show, Generic)
Post
    atom Int
    material String
    processing String
    params String
    image_url String
    reference String
    owner UsersId
    material_url String
    date UTCTime default=CURRENT_TIMESTAMP
    deriving (Show, Generic)
Comment
    owner UsersId
    post PostId
    date UTCTime default=CURRENT_TIMESTAMP
    text String
    deriving (Show, Generic)
|]
instance ToJSON Users
instance FromJSON Users
instance ToJSON Post
instance FromJSON Post
instance ToJSON Comment
instance FromJSON Comment