[FEAT] OpenIddict Module

We need to develop a new identity module that leverages [OpenIddict](https://github.com/openiddict) to serve as a more comprehensive alternative to the default `Elsa.Identity` module.

The goal is to create both a functional module and an illustrative example for users looking to extend or replace the default identity functionality in Elsa workflows. This will be useful for scenarios requiring more advanced identity management features than the current `Elsa.Identity` offers.

#### Requirements
- Leverage **OpenIddict** for authentication and authorization.
- Ensure modularity to support easy extension or replacement of the default identity module.
- Demonstrate how to integrate with external identity providers like **Auth0**.
- Provide clear documentation and example usage.

This would help extend Elsa’s identity management capabilities and serve as a reference for custom module development.