fix engine: allow task builder acquire move-only args

Tests: utest
commit_hash:4cdbd84cd01bd9962884c6939904c9d3bbef76be

Author: vtornikita

core/include/userver/utils/task_builder.hpp

@@ -125,13 +125,13 @@ inline auto TaskBuilder::MakeSpanFunctor(
 
 template <typename Function, typename... Args>
 auto TaskBuilder::Build(Function&& f, Args&&... args) {
-    using Task = engine::TaskWithResult<decltype(f(args...))>;
+    using Task = engine::TaskWithResult<std::invoke_result_t<Function, Args...>>;
     return BuildTask<Task>(std::forward<Function>(f), std::forward<Args>(args)...);
 }
 
 template <typename Function, typename... Args>
 auto TaskBuilder::BuildShared(Function&& f, Args&&... args) {
-    using Task = engine::SharedTaskWithResult<decltype(f(args...))>;
+    using Task = engine::SharedTaskWithResult<std::invoke_result_t<Function, Args...>>;
     return BuildTask<Task>(std::forward<Function>(f), std::forward<Args>(args)...);
 }
 

core/src/utils/task_builder_test.cpp

@@ -59,6 +59,17 @@ UTEST(TaskBuilder, Deadline) {
     EXPECT_TRUE(task.IsFinished());
 }
 
+UTEST(TaskBuilder, ForwardsMoveOnlyType) {
+    bool task_executed = false;
+    auto test_function = [&task_executed](std::unique_ptr<int>) { task_executed = true; };
+    utils::TaskBuilder builder;
+
+    auto ptr = std::make_unique<int>(42);
+    builder.NoSpan().Build(test_function, std::move(ptr)).Get();
+
+    EXPECT_TRUE(task_executed);
+}
+
 engine::TaskInheritedVariable<int> task_local_variable;
 
 UTEST(TaskBuilder, Background) {