Spawning from wanting to [run a load
test](https://github.com/element-hq/synapse-rust-apps/pull/397) against
the Complement Docker image of Synapse and see metrics from the
homeserver.
### Why not just provide your own homeserver config?
Probably possible but it gets tricky when you try to use the workers
variant of the Docker image (`docker/Dockerfile-workers`). The way to
workaround it would probably be to `yq` edit everything in a script and
change `/data/homeserver.yaml` and `/conf/workers/*.yaml` to add the
`metrics` listener. And then modify `/conf/workers/shared.yaml` to add
`enable_metrics: true`. Doesn't spark much joy.
9dae6cc595