- [x] separates modules into `fundamental`, `core`, `plugins`
- [x] optional modules with `@OptionalModule` decorator to install modules with requirements met(`requires`, `if`)
- [x] `module.contributesTo` defines optional features that will be enabled if module registered
- [x] `AFFiNE.plugins.use('payment', {})` to enable a optional/plugin module
- [x] `PaymentModule` is the first plugin module
- [x] GraphQLSchema will not be generated for non-included modules
- [x] Frontend can use `ServerConfigType` query to detect which features are enabled
- [x] override existing provider globally
liuyi