Implement dummy RPC for git push notifications
This change set implements a new server module called git_push_notifications
which is used by KAS and exposes a gRPC method to send git push events.
The ruby gem will expose that, because it's meant to be used by Rails.
This MR can already be merged so that we can develop rails independently from `agentk` should notify Flux about new commits w... (gitlab-org/gitlab#392852 - closed) and Hook into GitLab's internal/post_receive notifi... (#43 - closed).
The KAS module only logs a message with debug level - nothing else is implemented, yet.
Edited by Timo Furrer