The compile configuration has been deprecated for some time. api will behave similarly, whereas implementation will appear to be a runtime dependency to consumers.
This will require examining our public API so that we may correctly declare which dependencies are api. When a PR is made, an email should be sent to the dev@ and/or user@ lists warning that those consuming internal APIs (against best practice) may experience breakages if their own dependencies are not properly declared. Similarly, a release note on this topic could be helpful to those upgrading.