explicitParseFieldMaybe :: (Value -> Parser a) -> Object -> Key -> Parser (Maybe a)
explicitParseFieldMaybe p o key = case KeyMap.lookup key o of
  Nothing -> pure Nothing
  Just v  -> Just <$> p v <?> Aeson.Key key
explicitParseFieldMaybe :: (Value -> Parser a) -> Object -> Key -> Parser (Maybe a)
explicitParseFieldMaybe p o key = case KeyMap.lookup key o of
  Nothing -> pure Nothing
  Just v  -> Just <$> p v <?> Aeson.Key key
explicitParseFieldMaybe p o key = case KeyMap.lookup key o of
  Nothing -> pure Nothing
  Just v  -> Just <$> p v <?> Aeson.Key key