Guard against ParameterNotDeclaredException in parameter service callbacks (#718)
Guard against ParameterNotDeclaredException in parameter service callbacks (#718)

Fixes #705.

If the set_parameters() call fails, it's nice to be able to return a partial result.
Since there is no convenient method to obtain a partial result, we call set_parameters()
once for each parameter.

Signed-off-by: Jacob Perron <f862f167b85d41b225785c70d70808bc7337c1fe@openrobotics.org>

ros2/rclcpp,ros2/rclcpp