How to pass values dynamically via anotations

Problem/Motivation

In 8.x-2.0-beta4 version all changed to plugins. I'm trying to authenticate username and password while user login using resource_owner grant type. I tried with static values in plugin and it worked correctly. For multiple users how can i change the property for username and password dynamically. Annotations wont take dynamic values. Also oauth token endpoint and credentials will be different based on environment(like Dev, SIT, UAT, etc.). So we couldn't able to use this module