Create an indicator that we are low on space

re: https://github.com/adoptium/ci-jenkins-pipelines/issues/254#issuecomment-1054314294

It may be beneficial to visually indicate or through the API response that we are running low or out of space on disk. Currently TRSS ability to respond to queries degrades with no obvious notice of underlying problem. If we can warn of the issue, then we can intervene (either to purge data or clean up disk space manually).

Discussion issue, what are options for doing this, do we want to have this feature?

Start with the linked ci-jenkins-pipelines issue and its referenced comment, then review how TRSS currently behaves when disk space is exhausted. Decide whether the warning should be visual, part of the API response, or both; done requires an agreed option and implementation scope.

Written by the indexing model from the issue text.