Denote stale glucose (LOOP-927)

[ps2]

Update based on design review of DIY merge. https://tidepool.atlassian.net/browse/LOOP-927

[ps2]

• A single place for specification of glucose age time interval (LoopSettings?). Currently hardcoded at 15 minutes.
• HUDInterfaceController in WatchApp Extension should not display old bg data (second page of main watch app)
• Complications updated to show '---' when bg data is missing.
• Complications should register future timeline entries to allow bg data to go stale without updates from Loop.

[ps2]

Watch app and complications are now also showing Loop completion freshness using color. BG going stale is still denoted with dashes.

[nhamming]

A question about why there seems to be 2 different definitions of stale. Probably me missing something.

[nhamming]

Given this line, Line 62 isn't needed.

[darinkrauss]

LGTM. More only questions were around the use of LoopCompletionFreshness versus RecencyInterval, but @nhamming covered that. 🚀

[ps2]

Re-requested reviews, just to make sure my responses address your comments before merging.

[darinkrauss]

LGTM! 🚀

If RecencyInterval is specific to glucose values, then perhaps renaming this to something more specific might clarify the difference.

[ps2]

@darinkrauss It's not just for glucose data. It's also for pump data. It's about the age limit of data Loop is willing to use for creating a forecast. Maybe inputDataRecencyInterval?

[nhamming]

LGTM

[darinkrauss]

@ps2 Yes, something to distinguish it from the loop completion freshness. But, you can also do this in a later code change.

[darinkrauss]

LGTM!