Use guest scope as default

[escoand]

Currently the default scope of a new user is user.

This is not ideal when using oidc (and maybe also others) as auth because the user gets created with first login attempt. So the user has maybe more rights than desired.

With this change the default scope is changed to guest.

[satterly]

Why not just set USER_DEFAULT_SCOPES to read instead of read and write?

USER_DEFAULT_SCOPES = ['read']

[satterly]

Using this PR #1346 you could do ...

USER_ROLES = ['guest']

... which would set this default role for newly logged in users to "guest".

[escoand]

Why not just set USER_DEFAULT_SCOPES to read instead of read and write?

USER_DEFAULT_SCOPES = ['read']

I need all three builtin roles. So setting the default user scope to read forces me to create an additional user defined role for r/w. But I'm also fine with your PR.

[satterly]

Closing in favour of #1346