feat: git authors to be populated from users that sent the request

[kirederik]

Having a static GitAuthor would be great.

Not sure if this is possible; but even better would be a dynamic GitAuthor based on the identity that modified the promise resource-request.

ie - if user alice@my-corp.com ran kubectl apply -f my-promise-request.yaml then the commit to the GitStateStore would be attributed to alice@my-corp.com

That way commits to the GitStateStore become an audit log of who made which changes to the system without needing to enforce changes to the system going through a PR workflow that runs kubectl apply -f my-promise-request.yaml

Originally posted by @mrdavidlaing in #147