[4.x] Prevent calling notifications method on User model

[duncanmcclean]

This pull request fixes an issue when storing users in a database, where if you have a column called notifications, an error would be thrown during augmentation.

This was happening due to the Eloquent User model having a notifications method which returns a morphMany relationship, which our augmentation stuff doesn't know how to work with.

This PR fixes that by preventing the method on the User being called and falls back to checking the raw data on the user instead.

Fixes #9932.

[jasonvarga]

Things have changed a little in v5 so there might be some conflicts. Also, you should just add a notifications method to AugmentedUser rather than modifying AbstractAugmented. You can reopen targeting 5.x.