feat: Support AppGroups

[mrousavy]

Adds support for using AppGroups.

This stores MMKV instances in a shared AppGroup directory - it is mostly automatic.

To do this simply add your AppGroup to Info.plist, and don't pass a path to new MMKV(...) - MMKV will then automatically use the AppGroup path instead.

Related issues

• Fixes app groups: value undefined until restart #622
• Fixes App group enhancement introduced a breaking change (2.10.0) #627
• Fixes Crash reports after switching to use AppGroups due to 0xdead10cc #650
• Resolves Support for App Groups in MMKV 3.0.0-beta.6 #702

Related PRs

• Closes feat: If AppGroup defined in plist apply group dir. #703

Sorry @calism2 - your PR looked good, but I felt like moving the iOS-specific code into MmkvPlatformContext made more sense instead of cramming it into the shared cpp constructor.

[calism2]

It's not a problem that my original PR wasn't merged. The new approach is more readable and has better error handling. I tested both scenarios, and they work perfectly. I've added screenshots as well. Thank you for the quick PR merge.

With app group setup.

Without app group setup.

[mrousavy]

Thank you for testing @calism2!

But when do you see this error? Did you set AppGroup to something that is not a valid path?

[calism2]

Yes, the AppGroup needs to be added through Capabilities (you can add it for all, debug, or release), similar to Apple Pay. If you disable or remove the capability, the path won't be discoverable. As shown in the image, this setup only works for the debug version; you'll encounter an error in the release version. I tested this by removing the AppGroup capability from debug version.

[mrousavy]

gotcha - great!

[coopermaruyama]

nice! thanks for the contributions 🙂