Introduce a concept of step-metadata

[flosell]

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

If we had a separate concept of metadata, this could be used by build steps as well as LambdaCD itself to store such information and access it in a convenient way. It could also simplify the life of everyone trying to aggregate and visualize information about their builds in a custom way (see for example #84).

Some ideas on how it could look like:

Pipeline State:

{ :step-results { :step-results-like-before }
  :metadata     { :a-map-of-metadata }}

Sending metadata:

• As part of a step-result:

  { :status :success
    :metadata {:foo :bar }}

• Through the event-bus

  (event-bus/publish ctx :metadata-updated {:build-number 42 :step-id [1 2 3] :metadata {:foo :bar}

In the API and UI

• Build history could include all metadata
• UI could display some aspects of common metadata (maybe commits, ...)

[philwhln]

+1