The chart macro serves its images through the deprecated temp action from the legacy modules

The chart macro (xwiki-platform-chart-macro) builds the URL of the chart images it generates with the "temp" action (TempResourceAction), which is deprecated since 8.3 and only provided by xwiki-platform-legacy-oldcore since 14.3. A non-legacy module must not depend on legacy code: on a distribution without the legacy modules (e.g. the minimal distribution used by the docker functional tests), the chart image doesn't load.

The chart macro should use the "tmp" temporary resource API (TemporaryResourceStore and TemporaryResourceReference, from xwiki-platform-resource-temporary) instead, like the office viewer and the PDF export do.