Add support for GCP Shared VPC
What critical bug this MR is fixing?
Not fixing a bug per se, but is allowing to use a different project for the network api calls, for allowing the support of a network shared between multiple projects
How does this change help reduce cost of usage? What scale of cost reduction is it?
I don't think it will reduce costs but it will reduce the complexity for multiple projects that has to share the network (avoiding peer connections)
In what scenarios is this change usable with GitLab Runner's docker+machine executor?
In our use case we have a main project that managed a single VPC with multiple subnetworks that are then shared to other projects. In this way every project can communicate to the others without the need to maintain a peer connection and we can centrally manage the firewall policies that are allowed.
The change is backward compatible because it will always default to the main project name if no alternative one is provided. It is already in production in our organization for at least 2 years. I have already tried to merge the change but at the time the main project of docker-machine wasn't archived and the MR has been closed because only bug fixes were accepted at the time.