Allow for custom timeout in watch request

[pshchelo]

What do these changes do?

allow to set a custom timeout when making the GET ..?watch=true request to Kubernetes API if needed.

Description

Currently the timeout is always None, which we find to be a reason for issues like #204 .
With this patch controller authors may override the timeout passed by kopf to the underlying aiohttp session request by doing something like this in their controller code:

import kopf

kopf.config.WatchersConfig.session_timeout = 10.0

@kopf.on(..)
def handler(*):
    ....

The default behavior is not changed.

Issues/PRs

Issues: #204

Type of changes

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• The code addresses only the mentioned problem, and this problem only
• I think the code is well written
• Unit tests for the changes exist
• Documentation reflects the changes
• If you provide code modification, please add yourself to CONTRIBUTORS.txt

[zincr]

🤖 zincr found 0 problems , 0 warnings

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[pshchelo]

interestingly enough, coveralls job fails and reports as not covered lines I did not change/add...

[nolar]

Coveralls decrease is all fine. It fluctuates a little bit here & there.

Regarding the feature: Can you please refactor it to make the timeout as float instead of aiohttp.ClientTimeout?

Usage of aiohttp is a hidden detail of the current implementation and can change in the future. The session/client timeouts will probably stay, just differently implemented inside of kopf.clients.*.

UPD: Actually, Optional[float] = None, not just float.

[pshchelo]

Ack, sounds reasonable, will do