OZG-4097 itcase: Try out grpc mocking with wiremock

pom.xml

...loud/nachrichten/postfach/osiv2/ServiceIfOsi2Enabled.java

...richten/postfach/osiv2/config/ApiClientConfiguration.java

...n/postfach/osiv2/storage/Osi2BinaryFileRemoteService.java

src/main/resources/application-local.yml

src/main/resources/application.yml

...ichten/postfach/osiv2/OsiPostfachRemoteServiceITCase.java

...stfach/osiv2/extension/VorgangManagerServerExtension.java

src/test/resources/application-itcase.yml