Support for idField: 'id' in Feathers-Pinia When _id is Not Present

[Yehoshooafried]

Hi, first, thanks for your amazing library!

I ran into an issue while using Feathers-Pinia where my user entity has id instead of _id, causing authentication and store updates to fail. Feathers-Pinia seems to expect _id as the default identifier, which prevents users from being saved properly in the store.

To fix this, I had to manually map id to _id in my FeathersJS after hooks, which isn’t ideal. It would be great if Feathers-Pinia could properly respect idField: 'id' without requiring backend modifications.