add bbl config for external topgun-worker

[jamieklassen]

This is an external worker configured to register with the prod concourse but also have connectivity to its own dedicated bosh director for running topgun.

for this to work with the main pipeline, you need to override the BOSH_CA_CERT, BOSH_CLIENT, BOSH_CLIENT_SECRET and BOSH_ENVIRONMENT params for the topgun task, and run the job with the topgun tag.

The other thing is that the network topology means that the worker can connect to its director without an SSH key, so the topgun script probably doesn't need to add any ssh keys, and we won't need the BOSH_SSH_KEY param.

the create-topgun.sh script doesn't actually create anything, but it's a placeholder that you can run to at least make sure everything's wired properly and get the creds you need to mess around with stuff.

[jwntrs]

Should we be committing the bosh-deployment stuff in here?

[jamieklassen]

Good to ask the question, haven't explored whether bbl can generate it itself

[jamieklassen]

The key additions are topgun.tf and topgun.yml