Get github source information from environment when in a PR

[stevejpurves]

The build page on journals displays information on the source of the build. On a users machine this will use a git package to get the relevant information but this information is not correct when the cli is used in a PR via the action.

The proposed change is to look for GITHUB environment variables that will be available when running on a PR and use that information to populate the payload when creating the job, and falling back to the

We want to be able to provide consistent information on the source when on a PR, and when working locally. Hopefully we can recover everything we need on a PR, if not we should consider omitting it, if we know we are running from a PR that should be apparant in the information?