Impossible to fetch artifact for the build that is no longer in queue

Queue items are removed after build is finished. Current api allows only to fetch artifact for the queue item which makes this solution extremely inflexible.

To fetch artifact any time after build new api method should be introduced that would allow to specify build number and job name as input.

Start by tracing the current API for fetching an artifact from a queue item and compare it with the Jenkins build and job inputs described here. Define completion as an API method that accepts a build number and job name and can fetch the artifact after the queue item has been removed, with coverage for that post-build case.

索引モデルが issue の本文から書いたものです。