(DOCSP-27544): Flutter MapTo for realm models (#2530)

## Pull Request Info

Flutter MapTo for realm models

> **Note**
> 
> Intentionally not going into much detail in the description b/c i
think each of these topics would take up a lot of space. Whereas here I
just am going for a minimalist API description of this utility
annotations so that users can decide what they do with it.

### Jira

- https://jira.mongodb.org/browse/DOCSP-27544

### Staged Changes

- [Define a Realm Object Schema
(Flutter)](https://docs-mongodbcom-staging.corp.mongodb.com/realm/docsworker-xlarge/DOCSP-27544/sdk/flutter/realm-database/model-data/define-realm-object-schema/)

### Reminder Checklist

If your PR modifies the docs, you might need to also update some
corresponding
pages. Check if completed or N/A.

- [x] Create Jira ticket for corresponding docs-app-services update(s),
if any
- [x] Checked/updated Admin API
- [x] Checked/updated CLI reference

### Review Guidelines


[REVIEWING.md](https://github.com/mongodb/docs-realm/blob/master/REVIEWING.md)

Author: mongodben

examples/dart/test/define_realm_model_test.dart

@@ -37,6 +37,19 @@ class _Person {
 }
 // :snippet-end:
 
+// :snippet-start: map-to
+@RealmModel()
+@MapTo('naval_ship')
+class _Boat {
+  @PrimaryKey()
+  late ObjectId id;
+
+  late String name;
+  late int? maxKnots;
+  late int? nauticalMiles;
+}
+// :snippet-end:
+
 main() {
   test('Create a new schema version', () {
     // :snippet-start: schema-version

examples/dart/test/define_realm_model_test.g.dart

@@ -0,0 +1,10 @@
+@RealmModel()
+@MapTo('naval_ship')
+class _Boat {
+  @PrimaryKey()
+  late ObjectId id;
+
+  late String name;
+  late int? maxKnots;
+  late int? nauticalMiles;
+}

source/examples/generated/flutter/define_realm_model_test.snippet.map-to.dart

@@ -187,6 +187,26 @@ inverse relationships, and embedding objects within other objects.
 To learn more about how to define relationships in your Realm object schema,
 refer to :ref:`Relationships <flutter-client-relationships>`.
 
+.. _flutter-map-model-name:
+
+Map Realm Model to Different Name
+---------------------------------
+
+You can use the `MapTo <https://pub.dev/documentation/realm_common/latest/realm_common/MapTo-class.html>`__
+annotation to map a Realm object model to a different model name in Realm Database.
+This can be useful in the following scenarios:
+
+- Working with one realm from different Realm SDKs
+- Migrating Realm object models
+- Adhering to certain code style conventions
+
+If you're using Atlas Device Sync, the name that you map to corresponds
+with the :ref:`App Services Schema <schemas>` name.
+
+.. literalinclude:: /examples/generated/flutter/define_realm_model_test.snippet.map-to.dart
+   :language: dart
+   :emphasize-lines: 2
+
 .. _flutter-generate-realm-object:
 
 Generate the RealmObject