Add screenshot for poll interval from dashboard

[vipulgupta2048]

With the merge of balena-io-modules/rendition#1600, we are linking https://www.balena.io/docs/reference/supervisor/bandwidth-reduction/#side-effects--warnings page to the dashboard here:

To provide better context, we need to add a screenshot and write docs to help guide the users better.

Context: https://www.flowdock.com/app/rulemotion/public-s-community/threads/JQhGP_i2UgaNtnY62E7ZKScqePZ

[vipulgupta2048]

Hey @cywang117 Would you be willing to pick this up since you wrote the bandwidth document and possibly could help better explain the poll interval value? I be happy to help but would love if someone could take this patch up. Low priority.

[kb2ma]

@vipulgupta2048 , I think there are issues with this setting in several places. The problem with use of a screenshot on the bandwidth reduction page is that this setting is on the device/fleet configuration pages as well as the image download page, and the wording is different.

The text in the image download page "Check for updates every X minutes" is really generic. In the update PR for bandwidth reduction (#2476), we refer to this setting as "API Poll Interval". I suggest updating the image download page to something like, "API poll interval for device updates, in minutes". This should cue the user sufficiently to look for "API poll interval" on the doc link. We could also add a heading/anchor for the API poll interval entry on the bandwidth reduction page.

The text for this setting on the Device configuration page is "Define the balena API poll interval in milliseconds". This wording doesn't help describe what the setting does. It really should be the same as the image download page, "API poll interval for device updates, in milliseconds". Actually, use of milliseconds is error prone and too granular for this property. Minutes are OK; I might choose seconds.

So I think the solution for this setting involves several pieces, including a product call, and should be separate from #2476. I think the text in #2476 is pretty clear now. We can discuss text specifics on that PR.

[vipulgupta2048]

Sounds good to me, also I am sure we can do it async with the help of @myarmolinsky He is very motivated like me to link dashboard more closely to docs. And, any improvements we can do to the text or labels should be fine.
I also agree with keeping it separate from your current PR. Do make sure to post this on Zulip, so we can follow up