fix(adapter): throw helpful error for primitive arrays

[Azarcodex]

Fixes #1709

This PR improves the error message when json-server encounters arrays containing primitive values.

Previously, the server threw a low-level JavaScript error:
TypeError: Cannot create property 'id' on string 'role-1'

Now the server provides a clearer message explaining that arrays should contain objects so IDs can be generated.

Example valid format:
{ "roles": [{ "id": 1, "name": "role-1" }] }

This improves developer experience by making the issue easier to understand and debug.