Rules that have been applied:
- ERROR: Anything that is or may be problematic for the program to
continue running.
- WARN: Anything abnormal but definitely not critical for program
continuation, especially issues encountered when interacting with
clients (e.g. AAP).
- INFO: All state changes not corresponding to the "normal" processing of
individual data or messages/bundles, as well as further informative and
helpful messages. Includea errors that occur during normal data
processing.
- DEBUG: Messages to trace what happens with individual bundles and
other fine-grained information about internal processes.
At the moment, `LOG_ERRNO` always emits messages with the "ERROR" level.
We might want to change this in the future to better differentiate WARN
and ERROR in this regard also.
Closes: #140
Signed-off-by: Felix Walter <felix.walter@d3tn.com>