Document what debug log handling functions added via `debug_add_log_function` can rely on, especially wrt the objects being passed around
I'm implementing a custom debug log handler function that I register through the
gst_debug_add_log_function. My goal is to inspect the objects in certain ways and output the information obtained that way.
However I am encountering situations where the objects aren't obviously valid to inspect. One immediately apparent case is when the object has
ref_count = 0 for logs during the finalization of certain objects.
It would be great if documentation contained this information and informed users how to ensure the objects they look at are valid.