RFC-42: Deprecation of mirroring Third Party Dependencies via packages.atlassian.com

Whatever Atlassian decides to do here, please make sure that it is coordinated with plenty of advance notice, that you update the default build tooling to work with the new configuration, and that you provide examples of how to transition from the legacy configuration to the new setup.

This probably means releasing a new version of the Plugin SDK and/or AMPS (which are already broken for Platform 7 and in need of update anyway, as previously mentioned), as well as creating a page on DAC (not buried in a thread on the community forum) that describes the needed steps for a classical Maven project.