New Configuration MUST/MAY - Validate configuration file

[dol]

While reading the https://github.com/memorysafety/river/blob/main/docs/what-is-it.md#26---configuration requirements I noticed, that the possibility to validate a configuration file is missing. This would help prevent restart failures where the configuration file is invalid and the changes aren't applied to the server or the server won't even start due to a wrong configuration.

Other reverse proxies support this option.

• Apache apachectl configtest
• Nginx nginx -t
• Haproxy haproxy -c
• Caddy caddy validate

A typical Linux init script will check the config before performing a restart.

E.g.

• Apache
• Nginx
• Haproxy

It would be nice if River could follow this pattern and supports a built-in validation command line option.