Enable minimal changes with improved template logic

[tfoote]

The design of the TypeAdaptor shouldn't need this line changed.

publisher_ = this->create_publisher<std_msgs::msg::typesupport_protobuf_cpp::StringTypeAdapter>("topic", 10);

You should be able to use the

publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);

And the compiler template logic should be able to let you publish with either data type if you've included the right headers. So I think that we're slightly off on how we have the headers/templates setup to enable this.

[gonzodepedro]

I think the way to do this is using: RCLCPP_USING_CUSTOM_TYPE_AS_ROS_MESSAGE_TYPE.

[gonzodepedro]

I hacked a little bit our demo to use RCLCPP_USING_CUSTOM_TYPE_AS_ROS_MESSAGE_TYPE(std_msgs::msg::pb::String, std_msgs::msg::String);, by doing that I was able to construct the publisher with the custom type: publisher_ = this->create_publisher<std_msgs::msg::pb::String>("topic", 10);

I couldn't find a way to construct the publisher with the ROS_Type and make it automatically use the adapter.
Here is the publisher constructor documentation for reference. https://github.com/ros2/rclcpp/blob/3594381e04ae882b073875963c843c656fbf24f3/rclcpp/include/rclcpp/publisher.hpp#L57

[tfoote]

Yeah, I think you're right reading: https://github.com/ros2/rclcpp/blob/6f6b5f2e3608eafeadb908aa4f6eded5b38c3043/rclcpp/include/rclcpp/type_adapter.hpp#L86C50-L95

And https://ros.org/reps/rep-2007.html#defining-a-type-adapter

We can change it to allow declaring publish and subscribe on the adapted type if we inject the RCLCPP_USING_CUSTOM_TYPE_AS_ROS_MESSAGE_TYPE into the generated code. But we don't have the template metaprogramming to allow it to accept both types. Lets add that to the generation to allow people the simpler syntax with just declaring the adapted type and we can call that good enough.

[gonzodepedro]

Merged via eclipse-ecal#33