Some parts of the RdfClient class are blazegraph dependent. This is mainly the part that reads the response of write statements (SPARQL Update).

If we want to make the wdqs RDF code base usable in contexts other than blazegraph we need to refactor this logic in a way that response handlers can be plugged depending on the target backend.
The implementations that are currently backend specific (because not covered by the RDF/SPARQL standards) are:

• UpdateCountResponseHandler
• UpdateMetricsResponseHandler

AC:

• plugging in custom ResponseHandler implementations should be possible
• a backend agnostic implementation should be provided (returning fake metrics for the number of mutations)