fix(resolve): release cancelled previews and preserve task ownership

ui/flutter/lib/api/api.dart

@@ -81,6 +81,9 @@ Future<ResolveResult> resolve(ResolveTask resolveTask) {
   );
 }
 
+Future<void> releaseResolve(String id) =>
+    _parse<void>(() => _request('api/v1/resolve/${Uri.encodeComponent(id)}', method: 'DELETE'), null);
+
 Future<String> createTask(CreateTask createTask) {
   return _parse<String>(() => _request('api/v1/tasks', method: 'POST', data: createTask), (data) => data as String);
 }

ui/flutter/lib/api/model/resolve_task.dart

@@ -8,7 +8,10 @@ part 'resolve_task.g.dart';
 class ResolveTask {
   Request? req;
 
-  ResolveTask({this.req});
+  @JsonKey(includeIfNull: false)
+  String? id;
+
+  ResolveTask({this.req, this.id});
 
   factory ResolveTask.fromJson(Map<String, dynamic> json) => _$ResolveTaskFromJson(json);
   Map<String, dynamic> toJson() => _$ResolveTaskToJson(this);

ui/flutter/lib/api/model/resolve_task.g.dart

@@ -10,7 +10,8 @@ ResolveTask _$ResolveTaskFromJson(Map<String, dynamic> json) => ResolveTask(
   req: json['req'] == null
       ? null
       : Request.fromJson(json['req'] as Map<String, dynamic>),
+  id: json['id'] as String?,
 );
 
 Map<String, dynamic> _$ResolveTaskToJson(ResolveTask instance) =>
-    <String, dynamic>{'req': ?instance.req};
+    <String, dynamic>{'req': ?instance.req, 'id': ?instance.id};