attempt

data LoginData = LoginData {
    email :: Text
  , password :: Text
}

instance FromJSON LoginData
instance ToJSON LoginData

postUserLoginR :: Handler Value
postUserLoginR = do
  newLogin <- requireCheckJsonBody :: Handler Value
  let mEmail = fromJust $ parseMaybe (.: "email") newLogin :: Text
--from there, query the postgresql database and obtain a record (getBy) email