NXCALS-1339 Adds test cases for EntityClient
#Merge request template @acc-logging-team - please have a look for approval.
This MR is about testing our declerative feign configuration (via annotations) for the NXCALS service, http requesters.
It comes with the introduction of a basic wiremock configuration, to stup the actual endpoints and simulate a fake target for administering those requests and validate their behaviour based on some well defined expectations.
Currently only the EntityClient behaviour is coved by the effort provided on this MR.