zincati 0.0.12

Changes:

• strategy: uniformly use config labels
• strategy: cleanup unused logic
• contrib: add monitoring mixins
• rpm-ostree/status: detect and handle staged deployments
• docs: add more references to periodic strategy section
• strategy: add metrics to track updates strategy configuration
• ci: update travis toolchains
• docs/dev: describe the Cincinnati protocol used by Fedora CoreOS
• docs/update-strategy: make airlock a link
• github: create Dependabot config file
• docs/images: add a sequence diagram for locked reboots
• docs/dev: add some details on periodic strategy design

Tracker: https://github.com/coreos/zincati/milestone/9?closed=1