Automate deployment of private nextflu.org site

[joverlee521]

Currently, when a private nextflu build completes, we have to manually trigger the deploy private nextflu workflow with the AWS Batch job ID.

Now that the GH Action job stays attached and reflects the AWS Batch job status, it should be possible to automate the trigger of the deploy workflow after the builds completed.

I briefly looked into this today and realized this would require the pathogen-repo-build workflow to output the AWS Batch job ID to pass as an input to the deploy workflow.