Implement Signup Functionality through Fauna with Next.js 14 Server Actions

Now it's time to actually sign users up for our appliaction.

We'll implement the doSignup function that we created earlier. This function will run on the server with the 'use server' directive so we can instantiate a fauna client and call UserRegistration within this function.

From there we'll redirect the user to the /signin page which will error out because it's not implemented yet.