Add notification support

[simskij]

The operator should be able to send notifications upon starting and finishing test runs. To get a lot of options with little work, we should use https://github.com/containrrr/shoutrrr.

Configuration of notifications should be done by deploying a notification CR. Some kind of draft proposal of how this could look:

apiVersion: k6.io/v1alpha1
kind: K6Notification
metadata:
  name: k6-notification
spec:
  start:
    - some://shoutrrr/url
  finish:
    - some://shoutrrr/url
  error:
    - some://shoutrrr/url

[knechtionscoding]

@simskij Are we only looking for start, finish, error? Or are we looking for some other possible events? I'm not sure what all of the different states of a test are?

[yorugac]

Some additional input on this issue was here: https://community.k6.io/t/does-handlesummary-works-when-running-k6-in-distributed-mode/2532

[simskij]

Using shoutrrr, or some other go notification library (or apprise if you prefer to interface with python), in the operator to send notifications would be a decent low-effort start. What I'm thinking (or was thinking at least) is:

Start of test

• Where the results will be sent (if anywhere)
• Amount of runners/parallelism
• Which script (k8s ref is probably enough) was executed
• Which nodes the load generators was scheduled to
• Timing for when the generators went from paused to running

End of test

• When it completed
• Amount of successful runner jobs
• Amount of failed runner jobs
• Where the results were sent (if anywhere)

Notifying on the actual k6 metrics is likely best left to k6 itself.