add sanitized config endpoint

[jranson]

Description

This change adds a new sanitized config route on the listeners configured for the /config endpoint at /config/sanitized. The sanitized config provides a config output that is safe for sharing in Issues by anonymizing cache and backend names, as well as backend origin URLs, header injection values and authenticator data. See sanitize_test.go for exhaustive example input and output.

While implementing this capability, Codex found that 2 Options structs' Clone() functions were shallow-copying some elements. Since the running config is cloned and then the clone is mutated to generate the sanitized output, these options' Clones needed to be changed to a deep copy to ensure the sanitized config does not inadvertently mutate the running config.

Type of Change

• • Bug fix
• • New feature
• • Optimization
• • Test coverage
• • Documentation
• • Infrastructure

AI Disclosure

• • This contribution DOES NOT include AI-generated changes
• • This contribution DOES include AI-generated changes, and I have reviewed the relevant contributing guidelines.