feat(mobile): add three-state field serialization (#27231)

* bump to v7.22.0 and update patching

* gen client

* migrate mobile call sites

mobile/openapi/lib/model/stack_update_dto.dart

@@ -13,7 +13,7 @@ part of openapi.api;
 class StackUpdateDto {
   /// Returns a new [StackUpdateDto] instance.
   StackUpdateDto({
-    this.primaryAssetId,
+    this.primaryAssetId = const Optional.absent(),
   });
 
   /// Primary asset ID
@@ -23,7 +23,7 @@ class StackUpdateDto {
   /// source code must fall back to having a nullable type.
   /// Consider adding a "default:" property in the specification file to hide this note.
   ///
-  String? primaryAssetId;
+  Optional<String?> primaryAssetId;
 
   @override
   bool operator ==(Object other) => identical(this, other) || other is StackUpdateDto &&
@@ -39,10 +39,9 @@ class StackUpdateDto {
 
   Map<String, dynamic> toJson() {
     final json = <String, dynamic>{};
-    if (this.primaryAssetId != null) {
-      json[r'primaryAssetId'] = this.primaryAssetId;
-    } else {
-    //  json[r'primaryAssetId'] = null;
+    if (this.primaryAssetId.isPresent) {
+      final value = this.primaryAssetId.value;
+      json[r'primaryAssetId'] = value;
     }
     return json;
   }
@@ -56,7 +55,7 @@ class StackUpdateDto {
       final json = value.cast<String, dynamic>();
 
       return StackUpdateDto(
-        primaryAssetId: mapValueOfType<String>(json, r'primaryAssetId'),
+        primaryAssetId: json.containsKey(r'primaryAssetId') ? Optional.present(mapValueOfType<String>(json, r'primaryAssetId')) : const Optional.absent(),
       );
     }
     return null;