Introduce the concept of build-metadata

[flosell]

Problem

At the moment, all information about a build pipeline needs to be extracted from individual build steps:

• The build duration and build timestamps
• If the build was retriggered and from which one
• What triggered a build (was it a VCS commit, a manual user interaction, ...)
• That it received and processed a kill

Some of this could be better handled on a metadata-level for a build:

• e.g. to track when build has been active, when it has been sleeping (for duration calc); we could get rid of :has-been-waiting this way
• e.g. maybe random id generated at startup to determine if we restarted lambdacd (and with it potentially changed the underlying code) to warn users that retriggering might not be safe (Warn if retriggering a pipeline that has changed #139)?
  to identify which build was retriggered

Context

Related issues

• Introduce the concept of step-metadata Introduce a concept of step-metadata #86
• Redesign handling of pipeline-state/history Redesign handling of pipeline-state/history #131

[flosell]

Basic support implemented. Still todo:

• Documentation in wiki
  • https://github.com/flosell/lambdacd/wiki/Build-Context-(ctx)
  • https://github.com/flosell/lambdacd/wiki/Build%20Metadata
  • API doc coming up
• Support for retriggering
• Migrate functionality to metadata (current metadata is on step level)
• UI-Support for some frequently used metadata?
  • human readable build label
  • git commits? (pick up in UI: Display information about what triggered a build #159, UI: Display information about sign-offs #160 and Use build/step-metadata lambdacd-git#20)

[flosell]

Basic support implemented and ready for release. Moved additional features into separate issues.