[keycloak-user] Hiding the Login elements when we know that the user must Register

[Andrew Braae]

Summary
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We would like to improve the Keycloak experience for our new users by
removing all of the the Login elements (Email, Password, Remember me,
Forgot password, Login button) on the left hand side of the Keycloak page,
when we know that the user does not have an account in Keycloak already.

We would also like to pre-populate the Email field on the register page
with the user's email.

The thing that makes of these appear possible in our scenario is that the
user arrives at the Keycloak protected page via an invite link that
contains their email address.

Are these possible? How can we go about it?

More details
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We'd like to make the Keycloak experience simpler/more obvious for new
users.

In our scenario:
- we know the users email address, e.g. fred at gmail.com (it's in our own
application database)
- we have emailed the user a link to a Keycloak-protected invite page
- we allow Google, LinkedIn and email/password signin on the realm

Here are the current usability problems that we are seeing when the new
users follow their invite link.

1) Keycloak invites the user to enter their email and password to Log in.
However since we know their email, we could tell in advance that Login will
not work if they are not a Keycloak user already - they will have to
register. This is confusing to some subset of them, and they contact us
saying e.g. "it looks like I need a password, can you send it to me?".
(They don't think to click Register).

2) If they do click Register, then Keycloak allows them to enter any email
address. However, only fred at gmail.com will do, since that is who the invite
is for. Users rightfully feel confused/peeved that they have to type in
their email address, when they just clicked through from an email in that
same email account.

Any assistance gratefully appreciated.