Accessing Peer certificates in Access Control

### Why

- In our organization we use a custom Certificate Authority (CA) with Subject Alternative Names (SANs) for authentication and authorization. This is combined with mutual TLS (2-way).
- In the `AccessControl` implementation we need to have access to the certificate of the peer so that we can assign a role.
- Currently the `AccessControl` interface only provides a couple properties of the request metadata (depending on the node).

### Possible Implementation

- In our fork we have modified the `AccessControl` interface to permit passing an optional `Request` object in a backwards compatible manner. This allows for accessing more properties than just the peer certificate and can also be used for a variety of other authentication strategies.

I can open a draft PR with the required changes for further discussion.

Review the AccessControl interface and its current request-metadata properties first. Compare the proposed optional Request-based API with the existing authentication and authorization path; done means peer certificates can reach access-control decisions while preserving backward compatibility.

Written by the indexing model from the issue text.