Provides a cohesive Servant implementation of the OAuth 2.1 surface, covering discovery metadata, authorization and callback flows, token issuance, and dynamic client registration. The package models authorization codes, refresh tokens, and registered clients with PKCE enforcement, configurable persistence backends, and secure token generation helpers. Combined servers share state through MVars, integrate with `servant-auth-server` to mint JWT access tokens, and expose ergonomic helpers for embedding standards-compliant OAuth flows into Haskell applications.