Use jsonpath for getting/setting config values

[hasufell]

The current implementation is rather awkward:

ghcup-hs/lib-opt/GHCup/OptParse/Config.hs

Lines 187 to 215 in 4532d9a

	ShowConfig -> do
	liftIO $ putStrLn $ formatConfig $ fromSettings settings (Just keybindings)
	pure ExitSuccess
	(SetConfig k mv) -> do
	r <- runE @'[JSONError, ParseError] $ do
	case mv of
	Just "" ->
	throwE $ ParseError "Empty values are not allowed"
	Nothing -> do
	usersettings <- decodeSettings k
	when (usersettings == defaultUserSettings)
	$ throwE $ ParseError ("Failed to parse setting (maybe typo?): " <> k)
	lift $ doConfig usersettings
	pure ()
	Just v -> do
	usersettings <- decodeSettings (k <> ": " <> v <> "\n")
	when (usersettings == defaultUserSettings)
	$ throwE $ ParseError ("Failed to parse key '" <> k <> "' with value '" <> v <> "' as user setting. Maybe typo?")
	lift $ doConfig usersettings
	pure ()
	case r of
	VRight _ -> pure ExitSuccess
	VLeft (V (JSONDecodeError e)) -> do
	runLogger $ logError $ "Error decoding config: " <> T.pack e
	pure $ ExitFailure 65
	VLeft e -> do
	runLogger (logError $ T.pack $ prettyHFError e)
	pure $ ExitFailure 65

With a jsonpath library, this could be cleaner. See https://discourse.haskell.org/t/run-rfc-9535-jsonpath-queries-on-data-aeson/11067/13