Add iCloud Container backend

[landoncolburn]

Since the policy shift on the App Store, would it now be possible to have a iCloud App Container backup option? I will admit I'm not familiar with the Harmony codebase (I'm coming here off the Delta repo), but I would be willing to put in some work if needed to bring this feature. Just want to make sure there is not technical or otherwise limitations that I might not be privy to.

[ebelair]

Up ⬆️ Willing to help too!

[MisutaaAsriel]

I'm also interested in this. I don't know how much I could help, but I am willing to try. At the very least, there is interest.

Syncing to iCloud should, honestly, be fairly trivial compared to DropBox & Drive, since there's no authentication or setup processes involved. It seems to more just be a matter of enabling the entitlement for iCloud in Delta, and pointing Harmony towards the parent application's iCloud container. But… poking around that might require reworking harmony, since its structure for Services seems to expect things that are handled by iOS in iCloud's case.

Maybe these could just be stubs that return expected values when necessary? But I get the feeling this would be undesirable.

Alternatively, harmony could be bypassed in the case of iCloud, and Delta could write to iCloud directly, but I'm not sure if this is desirable either.