Split up formatting and writing

[whiskeysierra]

Right now the HttpLogger implementations do both, formatting the request/response data into some kind of text format and they also choose a concrete target for the data, usually a Slf4j Logger.

If we split those responsibilities up into two interfaces we could more easily add support for one of those concerns without changing the other.

As correctly mentioned by @lukasniemeier-zalando this could also mean we extract the condition (shouldLog) from the interface.

[lukasniemeier-zalando]

👍 maybe we should take the chance and easen the creation of the creation of a fully configured LoggingFilter