Allow configuring hostname in Docker container

[pavelhoral]

Summary

Current docker image bootstraps DS with hostname set to localhost - https://github.com/WrenSecurity/wrends/blob/b9af6473dd85fb55f62aa4adb4cab5389ff2fa4a/.docker/bootstrap/setup.sh#L36C4-L36C16. That is a sensible default for sandbox deployments. But we need to be able to setup real hostname in production deployments.

Expected Result (Behavior You Expected to See)

Be able to provide additional environment property to set server hostname.

[pavelhoral]

This might need additional research to provide arguments for why anyone should care about this setting... To be honest, I am not sure this configuration is that important in the end - I don't know if it plays any role in resolving server's own identity (e.g. for replication). It would be fine if this gets closed as invalid issue.