Automate release process

[minherz]

Description

Evaluate release-please bot vs. ad-hoc implementation to automate the release of the Sandbox versions.

Requirements

The release process should be automatically triggered on event of the tag placement. For the current version X.Y.Z, it should support both, a new version release i.e. X.Y.(Z+1) for fixes only and X.(Y+1).0 for features and fixes and a patch of the previous release i.e. X.(Y-1).(Z'+1) where X.(Y-1).Z' is the last version of the previous release.

The main branch should be synchronized with the latest version of the new release.

Each release has to have a dedicated branch which should be always up to date with the latest version for that release.

Additional operations such as updating provisioning/version.txt and version numbers in README.md files that are used for the walkthrough URL should be updated as well.

[NimJay]

Commenting because this is "near out-of-SLO":

• @minherz, thanks for the detailed description of this GitHub Issue — it's helpful!
• I'll leave this open since automating away manual processes is a team priority.
• Consider writing a one-pager for this effort (during our one-pager sprint). (If you do, please include a brief description of the current/today's release process. I'm guessing it's completely manual today.)

[NimJay]

@minherz I just found your Google-internal doc called "Cloud Ops Sandbox Release Process". That's helpful.
Our team should resume discussions in that doc.