DOCSP-29928 Serialization for Dart (#3235)

## Pull Request Info

Jira ticket: https://jira.mongodb.org/browse/DOCSP-29928

-
[Serialization](https://preview-mongodblindseymoore.gatsbyjs.io/realm/DOCSP-29928/sdk/flutter/realm-database/serialization/):
New page documenting serialization

### Reminder Checklist

Before merging your PR, make sure to check a few things.

- [x] Did you tag pages appropriately?
  - genre
  - meta.keywords
  - meta.description
- [x] Describe your PR's changes in the Release Notes section
- [ ] Create a Jira ticket for related docs-app-services work, if any

### Release Notes

<!--
- **Kotlin** SDK
- Realm/Manage Realm Files/Encrypt a Realm: Add information on
encryption for
    local and synced realms.
-->
**Flutter SDK**

- Serialization: Add new page for serialization of objects to and from
EJSON.

### Review Guidelines


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

examples/dart/test/person.dart

@@ -0,0 +1,15 @@
+import 'package:realm_dart/realm.dart';
+
+// :snippet-start: ejson-annotation
+class Person {
+  final String name;
+  final DateTime birthDate;
+
+  final int? age;
+  final double income;
+  final Person? spouse;
+
+  @ejson // annotate constructor to generate decoder and encoder
+  Person(this.name, this.birthDate, this.income, {this.spouse, this.age});
+}
+// :snippet-end:

examples/dart/test/pet.dart

@@ -0,0 +1,14 @@
+// :snippet-start: serialize-object-model
+import 'package:realm_dart/realm.dart';
+
+part 'pet.realm.dart';
+
+@RealmModel()
+class _Pet {
+  late String type;
+  late int numberOfLegs;
+  late DateTime birthDate;
+
+  late double? price;
+}
+// :snippet-end: 

examples/dart/test/serialization_test.dart

@@ -0,0 +1,156 @@
+import 'package:test/test.dart';
+import 'package:realm_dart/realm.dart';
+import 'utils.dart';
+import 'dart:typed_data';
+
+import './pet.dart';
+part 'serialization_test.realm.dart';
+
+@RealmModel(ObjectType.embeddedObject)
+class _Address {
+  late String street;
+  late String city;
+  late String state;
+  late String country;
+}
+
+@RealmModel()
+class _SerializeModel {
+  @PrimaryKey()
+  // ObjectID
+  late ObjectId id;
+
+  // UUID
+  late Uuid myId;
+
+  // Array
+  late List<String> listOfStrings;
+  late Set<int> setOfInts;
+  late Map<String, int> mapOfMixedAnyValues;
+
+  // Binary
+  late Uint8List requiredBinaryProperty;
+
+  // Boolean
+  bool isElectric = false;
+
+  // Date
+  late DateTime dateLastServiced;
+
+  // Document
+  late _Address? address; 
+
+  // Double
+  double milesDriven = 126.0;
+
+  // Int32 and Int64
+  int number32 = 900;
+  int number64 = 922393736854775807;
+
+  // String
+  late String licensePlate;
+
+  // Null
+  int? a;
+
+  // Missing encoders for RealmValue and Decimal 128, engineering ticket number: 
+  // RDART-1063 (https://jira.mongodb.org/browse/RDART-1063)
+}
+
+main() {
+  test('data types', () {
+
+    final config = Configuration.local([SerializeModel.schema, Address.schema]);
+    final realm = Realm(config);
+
+    final example = SerializeModel(
+      ObjectId(), Uuid.v4(), Uint8List.fromList([1, 2]), DateTime.utc(2024, 4, 10), 
+      '90ZXWYZL', listOfStrings: ['food', 'water'], setOfInts: {0, 1, 2, 3},
+       mapOfMixedAnyValues: {'first': 123 , 'second': 567}, 
+       address: Address("500 Dean Street", "Brooklyn", "NY", "USA"));
+
+    realm.write(() {
+      realm.add(example);
+    });
+
+    print(example);
+
+    EJsonValue exSerialize = toEJson(example);
+
+    print(exSerialize);
+
+    cleanUpRealm(realm);
+
+  });
+
+  test('serialize', () {
+
+    final config = Configuration.local([Pet.schema]);
+    final realm = Realm(config);
+
+    // create pet spider object
+    final spider = Pet('Jumping Spider', 8, DateTime.utc(2024, 4, 10));
+
+    realm.write(() {
+      realm.add(spider);
+    });
+
+    // :snippet-start: serialize
+    // Pass the object as a parameter to the method
+    EJsonValue serializeByParam = toEJson(spider);
+
+    // Call the method directly on the object
+    EJsonValue serializeWithCall = spider.toEJson();
+    // :snippet-end:
+
+    print(serializeByParam);
+
+    final birthDate = DateTime.utc(2024, 4, 10);
+
+    // make sure serialized value matches expected
+    expect(serializeByParam, {
+      'type': 'Jumping Spider',
+      'numberOfLegs': {'\$numberInt': '8'},
+      'birthDate': {
+        '\$date': {'\$numberLong': birthDate.millisecondsSinceEpoch.toString()}
+      },
+      'price': null,
+    });
+
+    // make sure two methods of serialization match
+    expect(serializeByParam, serializeWithCall);
+
+    cleanUpRealm(realm);
+  });
+
+  test('deserialize', () {
+
+    final config = Configuration.local([Pet.schema]);
+    final realm = Realm(config);
+
+    // create pet spider object
+    final spider = Pet('Jumping Spider', 8, DateTime.utc(2024, 4, 10));
+
+    realm.write(() {
+      realm.add(spider);
+    });
+
+    // Pass the object as a parameter to the method
+    EJsonValue serializeByParam = toEJson(spider);
+
+    // :snippet-start: deserialize
+    // Pass the serialized object to the method
+    final deserializeFromEjsonWithExplicitType = fromEJson<Pet>(serializeByParam);
+
+    // The method can also infer the object type
+    Pet deserializeFromEjson = fromEJson(serializeByParam);
+    // :snippet-end: 
+
+    print(deserializeFromEjson);
+
+    // make sure deserialized returns proper instance of Pet object
+    expect(deserializeFromEjson.type, spider.type);
+
+    cleanUpRealm(realm);
+  });
+}