Clarify interaction between cache configuration parameters, update interval and time-to-live values in the data

[testower]

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

Lamassu is missing high-level documentation on some configuration parameters. In some cases, the interaction of certain configuration parameters can lead to unexpected results, and seemingly inconsistent data.

Goal / high level use-case

Make it easier to understand how to configure lamassu correctly.

Describe the solution you'd like

• Document all configuration properties
• Create a matrix that demonstrates how caching configuration properties interact with update intervals and ttls in data
• Centralize caching configuration in a config service, so it can be checked at runtime, and display warnings for potentially "wrong" configuraitons

[hbruch]

In addition (or as a replacement for the matrix), I suggest to add a few use case examples, e.g. production use with spec conformant realtime feeds, with (mostly) static feeds, test instances with reduced updates,...