- added support for username and password
- added support for direct URI

- updated old gitlab.com URLs by new labs.etsi.org URLs.
- updated Context to use secrets generated by CockroachDB and NATS

- disabled event testing; operation works, but sometimes tests get stuck
- added dynamic wait for CockroachDB and NATS containers to start
- tuned grace shutdown period
- improved NatsBackend termination

- Added backend for NATS message broker
- removed unneeded test script