Create new BrightID account with a pre-existing profile

[UBIpromoter]

When a new user joins BrightID they should be given the option to sign up with a pre-exisitng account to simplify the onboarding if they would like. They can of course still create a new account under the current flow.

Something like this:

If they choose this option, we can grab their name and profile picture from that other account and offer to use those for BrightID as well. We should make it easy to change either of those fields if they are not what the person wants to use.

[UBIpromoter]

Perhaps there is also a smart way to control the User's BrightID password from this pre-existing profile.