Implement graceful termination and group-based app tracking

src/platform/linux/misc.cpp

@@ -249,6 +249,33 @@ namespace platf {
     lifetime::exit_sunshine(0, true);
   }
 
+  /**
+   * @brief Attempt to gracefully terminate a process group.
+   * @param native_handle The process group ID.
+   * @return true if termination was successfully requested.
+   */
+  bool
+  request_process_group_exit(std::uintptr_t native_handle) {
+    if (kill(-((pid_t) native_handle), SIGTERM) == 0 || errno == ESRCH) {
+      BOOST_LOG(debug) << "Successfully sent SIGTERM to process group: "sv << native_handle;
+      return true;
+    }
+    else {
+      BOOST_LOG(warning) << "Unable to send SIGTERM to process group ["sv << native_handle << "]: "sv << errno;
+      return false;
+    }
+  }
+
+  /**
+   * @brief Checks if a process group still has running children.
+   * @param native_handle The process group ID.
+   * @return true if processes are still running.
+   */
+  bool
+  process_group_running(std::uintptr_t native_handle) {
+    return waitpid(-((pid_t) native_handle), nullptr, WNOHANG) >= 0;
+  }
+
   struct sockaddr_in
   to_sockaddr(boost::asio::ip::address_v4 address, uint16_t port) {
     struct sockaddr_in saddr_v4 = {};