Draft: Unidirectional API (go broker)

Potential fix for #1 (closed)

I used go to implement a broker that translates regular HTTP process to the same external interface that is also used in !22 (closed).

Go as a language is much better suited for this because it is designed for concurrency (for example it has channels as a language primitive). No database polling is necessary.

On the downside this additional service that would need to be deployed along with the scheduler, making the overall architecture more complicated. Go also has the downside that our team is less experienced with it.