Inspire service for pushing records to HAL

To run unit and integration tests, just run

$ ./run-tests.sh

Currently, there's not yet CI/CD setup for this repo. This means that once the code for a new image is ready, you need to

docker build -t gitlab-registry.cern.ch/inspire/images/hal-push .

docker push gitlab-registry.cern.ch/inspire/images/hal-push