Upgrade Ember-Data/Ember-Data-Model-Fragments

[svogt0511]

In the last upgrade, ember-data had to be left at 4.6 because we are using the ember-data-model-fragments addon to handle complex data structures. There was no support for this addon in later versions. Since then, the Ember developers are working on providing a migration path.

Supposedly ember-data 4.6 will work with any ember v5. So for now we will continue working with that. A migration path is being implemented in 5.4 so we will see where they are with that as soon as we are done with the other ember upgrade tasks.

See the Technical Spec and Implementation Notes for more info.