Litestar-users

- add `LitestarUsersConfig.auth_backend_class` attribute.
- remove `LitestarUsersConfig.auth_backend` attribute.
- update role assignment/revocation route handlers to use HTTP PUT.

- update the package to work with `litestar` v2.1.1
- drop `pydantic` dependency.

- fix `retrieve_user_handler` to use the same db session used in dependency injection.

- fix unset default argument on `BaseUserService`.
- fix unset `UserCreateDTO` fields to be excluded from user creation.

- update (harden) authentication algorithm.
- remove built-in `OpenAPIConfig` instance.

- add `argon2-cffi` dependency.
- default password hashing scheme to `argon2`.