webcfg: add header and meta refresh for main page

[duhow]

Adds a meta refresh in main / website to reload every 15 seconds on visit.

[iranl]

Wouldn't a async javascript call be a cleaner solution instead of forcibly refreshing the entire page every 15 seconds?

[duhow]

Anything works, sure. I'll check. Would you like to keep the custom header code anyway?

[technyon]

Agree, wouldn't this reset your viewport to the top of the page every 15 seconds?

I'm not sure if adding javascript and async calls is really worth it, I mean the header part only display basic information that rarely changes, unless you're pairing a device. Maybe we should send the header as long as no device is paired?

[iranl]

See 85e8f9c for proposal using async javascript.

Updates every 3 seconds until:
-MQTT is connected
-Latest firmware is known (if update checking is enabled)
-Lock is paired and state is known (if lock is enabled)
-Opener is paired and state is known (if opener is enabled)

I do find the idea by @duhow usefull enough to implement something to tackle this as I find it annoying while pairing and/or restarting Nuki Hub that these values don't auto refresh, at least until a valid value is known.

Propose async javascript is a better solution than refreshing the entire page as the viewport won't reset and it can thus be set to refresh much more often/quickly without interupting the user.

[technyon]

ok sure let't go for it then.

[technyon]

So this is ready to be merged?

[iranl]

LGTM and tested without problems on my end.

@duhow You ok with the current state?

[duhow]

✅ As a first iteration looks good, web content gets updated.
⚠️ However, upon restarting, the second update gets undefined JS state...

Ideally you may want to fully change the main page content to be rendered with JS, but does not need to be on this PR.

[duhow]

Thank you all! 😄

[iranl]

✅ As a first iteration looks good, web content gets updated. ⚠️ However, upon restarting, the second update gets undefined JS state...

Fixed in #389