This updates the Ember edition setting to Octane, which I removed from #8319
because it required the template-only Glimmer components setting to be turned
on, which this does. These changes to templates accommodate that setting.
This updates to Ember 3.16 but leaves Ember Data at 3.12 so we don’t need
to use the model fragments beta. It can be reviewed on a commit-by-commit
basis: blueprint updates, fixes for test failures, and the removal of
now-deprecated partials.
It’s not a true update to Octane as that would involve turning on template-only
components by default, which breaks various things. We can accomplish that
separately and then add the edition setting to package.json.
