GBFS update delta service

[testower]

Is your feature request related to a problem? Please describe.

The entity updaters are very complex and contain a lot of logic to figure out what has changed from one update to the next. The code is not easy to read and is not very well tested. In addition, we could foresee the need for a general solution to computing the delta of gbfs updates.

Goal / high level use-case

Create a new service within lamassu to compute the delta of gbfs updates.

Describe the solution you'd like

Describe alternatives you've considered

Additional context