stretch: deploy changes based on whether or not diff affects stateful services

Created by: jhchabran

Problem

See this part of the Miro board

Some services which are stateful introduce a silent interruption of service when deployed, i.e deploying gitserver will prevent some search results to happen. As such, the current approach is to deploy those on a daily basis and to exclude them from continuous deployment.

RFC 586 aims to rely on a cron-job in order to address this, postponing the deployments to limit disruption toward our customers.

Expected Outcome

• We manage to find a way to confidently distinguish between the PRs that are not affecting those services from those who do. This enables us to identify PRs which are eligible for a continuous deployment where we can keep going with RFC 592.