Simple row serialization?

Hi,

I'd like to implement some simple data logging via triggers on a small
number of infrequently updated tables and I'm wondering if there are
some helpful functions, plugins or idioms that would serialize a row
(received for example in a AFTER INSERT trigger) into a string that I'd
store in the log table. There's a limited number of field types
involved: varchars, integers and booleans. I'm not looking for anything
fancy, comma-separated string result will be just fine; Even better,
something like a dictionary ("field_name":"field_value",...) would be
nice. The reason for trying to do it this way is that I don't want to
create separate log tables for every table I wish to log.