Add preferred_username to local static passwords

[cldfzn]

Preflight Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for an issue that matches the one I want to file, without success.

Problem Description

We would like to use preferred_username as the claim of choice for some of our operations, but it does not seem that we can have that claim filled when using a static password based client.

Proposed Solution

Add the preferred_username claim to match the username attribute on static password based clients or make claim mapping available for us to populate the token with the pre-filled data.

Alternatives Considered

No response

Additional Information

No response

[ioboi]

I would like to work on this issue.