Feature Request: Pre-fill username in first login screen OIDC auth, or skip first login screen

Overview of the Feature Request
We are using the OIDC authprovider and find that in the first login screen/form, the username is blank, even though it is part of the standard OIDC claim. We would like the username to be prefilled, just like the Given Name, Family Name and Email fields.

Ideally, but this may be a separate issue, we would like to skip this first login screen altogether.
The OIDC connection is a connection to our institute's AD, so we can be confident this 'default' information is correct.
Having the form only provides room for error and may be confusing to our users.

See also: issue #6690

What kind of user is the feature intended for?
Curator, Depositor

What inspired the request?
The use of a OIDC connection.

What existing behavior do you want changed?
The first login screen: it should either be prefilled completely, or there should be a setting to skip that screen entirely.

Any open or closed issues related to this feature request?
This is effectively a reopening of issue #6690, which was closed because it was opened before 2020.

Are you thinking about creating a pull request for this feature?
I might, but I'm not familiar with the code base enough to fix it quickly yet.

Start by tracing the OIDC auth provider flow that creates the first login screen, then compare the requested behavior with issue #6690. Done means either the username is prefilled from the OIDC claim and the other fields remain correct, or a supported setting skips the screen entirely; clarify which option is intended before implementation.