Merge pull request #1103 from strongloop/doc/forceId-3.x

Describe the change of forceId

Author: bajtos

3.0-RELEASE-NOTES.md

@@ -154,3 +154,36 @@ var johndoe = new User({ name: 'John doe', age: 15, gender: 'm'});
     ```
 
 See [related code change](https://github.com/strongloop/loopback-datasource-juggler/pull/1084) here.
+
+## Users cannot provide a custom id value when id is auto-generated
+
+For security reason, the default value of config variable `forceId` is set to
+`true` if a model uses auto-generated id. It means creating/updating instance
+with a given id will return an error message like:
+
+```
+Unhandled rejection ValidationError: The `MyModel` instance is not valid.
+Details: `id` can't be set (value: 1).
+```
+
+You can change `forceId: false` in model.json file to disable the check, eg:
+
+Change config in `common/models/MyModel.json`:
+
+```json
+{
+  "name": "Product",
+  "forceId": false
+}
+```
+
+Then create a new instance with given id:
+
+```js
+MyModel.create({
+  id: 1,
+  name: 'test',
+}).then(function(modelInstance) {
+  // Get the modelInstance with id = 1.
+});
+```