WIP - Testability/Quality of Server/Watcher/Builder/Proxy

I set out to write tests and improve our proxy, as it does not work correct today. We have been chasing our tails a bit on these code-paths. The solution is to increase high value test coverage.

As I began I realized this part of the code-base has not be adapted to the project architectural guidelines, this PR aims to remedy this.

- [x] refactor builder
- [ ] refactor watcher
- [ ] refactor ExpressServer
- [ ] test builder
- [ ] test watcher
- [ ] test ExpressServer