Error handling: sign-up: if user exists throw error

[christer]

Currently it goes to the lobby

Solution:

• Create table user_ids that only has the user_id of all users, where anyone can look up
• Add trigger and function to copy from the auth.users table
• If exists, redirect to signin and give error ":O you tried signing up with an account that already exists"
• Prefill the email field in sign-in form