Represents a debug message the user might want to print out for logging
while debugging or whatnot. These will always come by way of the 'error'
channel on streams or other event emitters. It's completely fine to
ignore them, as some will just be verbose logging info, but they may
help figure out what's going wrong. Support may also ask you to catch
these channels, which you can do like so:
subscription.on('debug', msg => console.log(msg.message));
These values are not guaranteed to remain stable, even within a major
version, so don't depend on them for your program logic. Debug outputs
may be added or removed at any time, without warning.