We should allow the user to define a custom metrics port. At first this should be via the configuration file, but eventually it should be done via an in-game window.

I would like to be able to startup OpenRCT2 with a known save game and ensure the plugin runs properly. If it's possible to replay a game session, it would be great to ensure the plugin works over time.

We should export the network metrics: number of connected players, their observed latencies, commands and money spent by each player.

We should add the ticks and month age as exported metrics, otherwise you can't easily identify a paused or fast forwarded game.

The Prometheus text format is being rendered in an adhoc fashion by the TCP server handler. This should be querying the metrics from a registry-like object, which would make it easier to formalize rendering TYPE, HELP, and series lines.

Should export metrics from each ride. We can start with excitement, nausea, and intensity and work our way up from there.

This will likely require changes to the collector pattern to support multiple series per metric type.

If there's interest from other developers, we could allow for external scripts to expose their own metrics (eg, a Twitch plugin could have metrics for responding to chat commands).

1. What APIs do these developers need? We'd probably want to expose the fundamental types and the default registry at the very least.
2. How should we handle OpenRCT2 plugin loading order? Other plugins may load before us. AFAICT, there's no hook for plugins loaded, so not a great way to signal to other plugins that we're now available. Pooling for our global could work, but not great.
3. Allow users to disable metrics from specific plugins. We might be able to do this as part of a configuration UI (and initially the configuration file)