chore: Cancellable coroutines (#2180)

Add a wrap for `boost::asio::yield_context` to make async operations
cancellable by default. The API could be a bit adjusted when we start
switching our code to use it.

src/util/Coroutine.cpp

@@ -0,0 +1,90 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "util/Coroutine.hpp"
+
+#include <boost/asio/any_io_executor.hpp>
+#include <boost/asio/bind_cancellation_slot.hpp>
+#include <boost/asio/cancellation_type.hpp>
+#include <boost/asio/error.hpp>
+#include <boost/asio/post.hpp>
+#include <boost/asio/spawn.hpp>
+
+#include <cstddef>
+#include <memory>
+#include <utility>
+
+namespace util {
+
+Coroutine::Coroutine(boost::asio::yield_context&& yield, std::shared_ptr<FamilyCancellationSignal> signal)
+    : yield_(std::move(yield))
+    , cyield_(boost::asio::bind_cancellation_slot(cancellationSignal_.slot(), yield_[error_]))
+    , familySignal_{std::move(signal)}
+    , connection_{familySignal_->connect([this](boost::asio::cancellation_type_t cancellationType) {
+        cancellationSignal_.emit(cancellationType);
+        isCancelled_ = true;
+    })}
+
+{
+}
+
+Coroutine::~Coroutine()
+{
+    connection_.disconnect();
+}
+
+boost::system::error_code
+Coroutine::error() const
+{
+    return error_;
+}
+
+void
+Coroutine::cancelAll(boost::asio::cancellation_type_t cancellationType)
+{
+    if (isCancelled())
+        return;
+    familySignal_->operator()(cancellationType);
+}
+
+bool
+Coroutine::isCancelled() const
+{
+    return error_ == boost::asio::error::operation_aborted || isCancelled_;
+}
+
+Coroutine::cancellable_yield_context_type
+Coroutine::yieldContext() const
+{
+    return cyield_;
+}
+
+boost::asio::any_io_executor
+Coroutine::executor() const
+{
+    return cyield_.get().get_executor();
+}
+
+void
+Coroutine::yield() const
+{
+    boost::asio::post(yield_);
+}
+
+}  // namespace util