The OIDC Authenticator uses code for formatting user names that's also present in the confluence and ldap extensions.
A module has been created to deduplicate this code: https://www.xwiki.org/xwiki/bin/view/documentation/extensions/dev/user-common/user-common-formatter/
See the forum discussion: https://forum.xwiki.org/t/request-for-a-new-contrib-repository-for-a-user-and-group-name-formatter-and-cleaner/18201
