### What?
Moved the logic for copying the data.id to data._id to the mongoose
adapter.
### Why?
If you have any hooks that need to set the `id`, the value does not get
sent to mongodb as you would expect since it was copied before the
beforeValidate hooks.
### How?
Now data._id is assigned only in the mongodb adapter's `create`
function.
BREAKING CHANGES:
When using custom ID fields, if you have any collection hooks for
beforeValidate, beforeChange then `data._id` will no longer be assigned
as this happens now in the database adapter. Use `data.id` instead.
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