GRDB support, push support & schema migration documentation

[yqiang]

Hi folks,

I'm investigating various options for adding sync to my iOS app and found this promising project. I've got a few questions which I couldn't find answers to in the existing documentation:

• If my app is currently using GRDB, what's the best way to get started with enabling sync?
• How can sync be triggered via silent, background push notifications on iOS, similar to how CloudKit works?
• What are the recommendations for how to do schema migrations? I saw a section about FK's, but it wasn't totally clear how this library supports it (if at all).

Looking forward to testing this out!