Ruby client library and CLI tool for the OPNsense REST API

It is meant as a replacement for net-mgmt/py-opn-cli. It provides:
- An HTTP client with SSL, redirect handling, and API key authentication
- UUID/name resolution for ModelRelationField and CertificateField references
- Service reconfigure orchestration with configtest support
- OPNsense selection-hash normalization
- A CLI tool for interactive API access
- A resource registry that abstracts away inconsistent endpoint naming
