Docs are showing examples of implementation of betterAuth using auth-client, which is great, simple, with callbacks to handle errors, etc. BUT it allows only for client side validation which is NOT SECURE as you can bypass it easily and harm server, db, etc. How do I add server side validation of all the fields for signUp/SignIn? I know I can use auth.api.(whatever) but then I need to handle all the errors and other stuff by myself. Am I missing something? Does betterAuth library makes some server side validation internally? Or I have to choose between simplicity of implementation and security ? Thank you