Use "name" claim in OIDC SSO for display name

When creating a user from SSO, the code uses the OIDC claim "preferred_username" for the username, which is usually more of a login username than a display name, which is more how vaultwarden uses it. Entra ID, for instance, uses UPN, which might just be the email address.


The OIDC spec indicates the field "name" as more fitting for a display name:


So we could either:
• Use the "name" claim in the code, with "preferred_username" as a fallback
• Make a config field to set the claim to be used for username definition

Feel free to comment you insights on this idea.