JSLT [1] supports powerful transformations on JSON data. Possible use cases would be the conversion of existing results to conform to breaking changes in ORT's data model or the manipulation of results to generate test data. I played around with JSLT when I changed the data format for vulnerabilities in the Advisor module. As I found it useful, I thought I could share it. If you think, this is out of scope, just close this PR.

There is one limitation, however: JSLT does not handle tags in YAML and simply drops them. This is a problem with ORT result files because Jackson uses such tags to deal with class hierarchies. Currently the configuration of scan result storages makes use of this mechanism; so a manual post-processing of result files is necessary.

As an example for a JSLT transformation that could be applied, here is one that converts the advisor result section from the old format of vulnerabilities to the new one (as introduced in #3823):

{
  "advisor": {
    "results": {
      "advisor_results": {for(.advisor.results.advisor_results)
        .key: [for(.value) {
          "vulnerabilities": [for(.vulnerabilities) {
            "id": .id,
            "references": [
              {
                "url": .url,
                "severity": string(.severity)
              }
            ]
          }],
          "advisor": .advisor,
          "summary": .summary
        }]
      },
      * : .
    },
    * : .
  },
  * : .
}

[1] https://github.com/schibsted/jslt