refactor(simplification): non-essential code removed or moved to server

The same set of changes as with other plugins.

No tests yet!


Breaks compatibility with [lamassu/lamassu-server](https://github.com/lamassu/lamassu-server)@[v0.6.2](https://github.com/lamassu/lamassu-server/commit/c6f53b5f087c61ca30046890a8c9d2fc73320acd)