Assert on coordinator state in e2e tests

[luckysori]

The e2e tests currently do an okay job at checking that certain flows work for the app. They do not directly verify if those flows work for the coordinator.

For example, when e2e_open_position passes, we don't know if the coordinator's position was updated correctly. If there is a bug, this might have an impact on metrics and perhaps even future trades.

It might be a pain to expose all the necessary information via the coordinator's HTTP API, so we could use something like PostgREST to look at the coordinator's DB directly.