[PR] Add the silent spy-handlers for the raw events, no persistence

[kopf-archiver]

A pull request by nolar at 2019-05-29 15:07:41+00:00
Original URL: zalando-incubator/kopf#86
Merged by nolar at 2019-06-02 16:53:40+00:00

Issue: closes #30

Add the simplistic event-handlers for spying on the low-level events of other resources,
not belonging to the operator (and not storing any status fields or finalizers or so).

The syntax is:

import kopf

@kopf.on.event('zalando.org', 'v1', 'kopfexamples')
def event_fn(event, **kwargs):
    pass

The difference from the regular handlers is documented in the docs/handlers.rst (see the changed files). Briefly:

• No state storage on the objects.
• No annotations or finalizers added to the objects.
• No k8s-events posted for the activity (only the stdout/stderr logs).

Altogether, this means "silent" — the objects do not know they are being watched & handled (i.e. spied).

Checklist:

• Tests.
• Documentation.