HTTP error 413 Payload too large

Alertmanager can encounter HTTP 413 status code coming from the bottle web listener in prometheus2canopsis.

28/12/2020 10:57:39level=error ts=2020-12-28T09:57:39.578Z
caller=dispatch.go:309 component=dispatcher msg="Notify for alerts failed"
num_alerts=1025 err="canopsis/webhook[0]: notify retry canceled due to
unrecoverable error after 1 attempts: unexpected status code 413:
http://prometheus2canopsis.example.lan:8080/webhook"