Allow custom handle during account creation #693

Currently if you try to use a custom handle during sign up you get "Custom domains can be set up in Settings" under the handle input and if you ignore that and try to create the account still you get "Handle cannot contain dots. You can set up a custom domain handle after creating your account.". However we do allow custom handles from the get go when migrating an account. We should allow it during brand new account creation too. We can either have a step to verify that the handle is actually valid or we can just let the user create the account without it initially having a valid handle or perhaps both: Have a step to verify the handle and allow users to push through that if they have issues with it for whatever reason.