Export role details of each ApplicationRegistration from Authz API

This MR introduces the a new Authz API client that has been generated based on the OpenAPI (Swagger) Spec: https://authorization-service-api.web.cern.ch/swagger/index.html

This allows us to easily adapt to schema changes in the API (e.g. new endpoints for resource portal) by re-running the code generation. It is also safer compared to the current, hand-written API client implementation.

The new API client is then used to implement the applicationregistration_export controller which regularly exports the roles of each ApplicationRegistration from the Application Portal.

The most important files to be reviewed are the ones from the last commit (README.md, operator.go, applicationregistration_export_controller.go)