Generic debug topic / message

[rshanor]

Description

Please let me know if a similar feature already exists. I am imagining some generic message type.

# Generic message definition
string topic
string type
string serialized_message

The recorder could subscribe to a topic like /rosbag2_recorder/generic_message_topic

Then I could write code like.

generic_publisher.publish(Foo(), "/myFooTopic", "std_msgs/Foo")
generic_publisher.publish(Bar(), "/myBarTopic", "std_msgs/Bar")

In the log, this would look like normal messages.

Topic information: Topic: /myFooTopic | Type: std_msgs/Foo | Count: 1
                             Topic: /myBarTopic | Type: std_msgs/Bar | Count: 1

It would make it super easy for me to populate my log with a bunch of debug data without having to pass around a bunch of publishers. Thoughts?