Allow client to specify intent to login vs register

[michielbdejong]

A client can show a 'login or register' button.
After that, the IDP would still have to show two options, one to log in and one to register.
Instead, a client may prefer to show one 'login' button and one 'register' button.
When they do that, it would be nice if the page they land on at the IDP, that option is pre-selected.
Of course, the IDP would probably still allow to switch between login vs register on there, but at least it saves a click.

See also the corresponding issue here: nodeSolidServer/solid-auth-client#102

[elf-pavlik]

see solid/solid-oidc#77

[michielbdejong]

Maybe we could use prompt=create from https://openid.net/specs/openid-connect-prompt-create-1_0.html

[josephguillaume]

If I understand correctly, this is related to the need to persist state through the login process. Apparently solid-client-authn-js currently can't do this (inrupt#950). Is this a blocking issue here too?

Edit: sorry, just realised URL params do persist through the redirect url. The linked issue for solid-client-authn-js is still relevant, as the example cites "to start with registration page rather than login page"