TF-2302 Fix edit identity

Signed-off-by: dab246 <tdvu@linagora.com>
(cherry picked from commit 526a85b3d41c312dc1870d05673962a31b2c8796)

model/lib/identity/identity_request_dto.dart

@@ -12,8 +12,8 @@ part 'identity_request_dto.g.dart';
 
 @IdentityIdNullableConverter()
 @SignatureNullableConverter()
-@JsonSerializable()
 @UnsignedIntNullableConverter()
+@JsonSerializable(explicitToJson: true, includeIfNull: false)
 class IdentityRequestDto with EquatableMixin {
 
   final String? name;