This Jenkins plugin adds a very simple menu to create service users for use with e.g. the Authorize Project plugin.
Go to Manage Jenkins and then Service Users. You can add/remove service users on that page.
Note: whether these service users can actually be impersonated (e.g. via Authorize Project plugin) depends on the configured security realm. Some security realms do allow impersonating users that are only present in Jenkins' own database, others don't.
Starting a development Jenkins instance with this plugin: mvn hpi:run
Building the plugin: mvn package