OZG-4097 itcase: Try out grpc mocking with wiremock

pom.xml

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

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

src/test/resources/wiremock/proto/binaryfile.model.proto

src/test/resources/wiremock/proto/binaryfile.proto

src/test/resources/wiremock/proto/callcontext.proto

...test/resources/wiremock/proto/clientattribute.model.proto

src/test/resources/wiremock/proto/clientattribute.proto

src/test/resources/wiremock/proto/command.model.proto

src/test/resources/wiremock/proto/command.proto

src/test/resources/wiremock/proto/common.model.proto

src/test/resources/wiremock/proto/file.model.proto

src/test/resources/wiremock/proto/file.proto

src/test/resources/wiremock/proto/forwarding.model.proto

src/test/resources/wiremock/proto/forwarding.proto

...est/resources/wiremock/proto/route-forwarding.model.proto

src/test/resources/wiremock/proto/route-forwarding.proto

src/test/resources/wiremock/proto/statistic.model.proto

src/test/resources/wiremock/proto/statistic.proto

src/test/resources/wiremock/proto/system.model.proto