Add configurations for Cilium Envoy to handle authentik forward authentication

**Is your feature request related to a problem? Please describe.**
Currently, integrating authentik's forward authentication with Cilium's Envoy proxy requires manual configuration. Providing predefined configurations would streamline this integration process.

**Describe the solution you'd like**
Include default configuration templates or guidelines in the authentik documentation to facilitate seamless integration with Cilium's Envoy proxy.

**Describe alternatives you've considered**
Manually configuring Envoy based on existing authentik documentation. However, this approach can be error-prone and time-consuming.