Add a way for processors to run code after the line is logged

[underyx]

From IRC:

[14:08:07]  <underyx>	@hynek would it somehow be possible for a processor to print something after the rendered line is printed?
[14:08:19]  <underyx>	it seems impossible to me right now but maybe you know of a way
[14:08:44]  <underyx>	specifically I'd like to print multiline request/response bodies after the actually log line
[14:09:46]  <hynek>		underyx: yeah sadly it’s impossible because loggers run last.  we'd need some kind of post-log hook
[14:10:05]  <underyx>	can I open an issue for that or do you consider it out of scope?
[14:50:21]  <hynek>		I think that would be useful.  Maybe it should also get the result of the logger call