Storyboards should recognize when access token is set elsewhere

[friedbunny]

When using storyboards to instantiate a map view, it isn't always desirable to set the access token there. We should do the legwork to check if the access token is set elsewhere (perhaps as a global) and present the pretty blue "everything is OK!" screen if it is actually working.

Per chat with @1ec5:

Not sure if designable code can look at environment variables, but it could be made to read a resource file that wouldn't be checked in. Lots of hoops to go through then.

But this isn't really specific to storyboards. Code works the same way; best to use a dedicated public token I suppose.

[friedbunny]

There is also the (edge?) case where developers may not be using Mapbox tiles and thus not require a Mapbox access token.

[1ec5]

See also #1553: from within a build script, it’s easier to add the access token to the Info.plist (using plutil -insert) than to code or a storyboard (where you’d have to do some amount of parsing). But I think Treble demonstrates that the ignored access token file approach makes sense too.

[1ec5]

#1553 (comment) provides a sample Run Script build phase. I think I’d be comfortable putting that script in a help topic on mapbox.com and linking to it from the installation guide, for developers hesitant to make even their public access tokens public.

[friedbunny]

Action on this happening in #1613.