Convenience extension for running ModelActor code in the background

ModelContainer+runNonisolated.swift

extension ModelContainer {
    // non-throwing version
    nonisolated func runNonisolated<ResultType, ActorType: InitWithModelContainer>(
        action: @Sendable (_ actor: ActorType) async -> ResultType
    ) async -> ResultType {
        let actor = ActorType(modelContainer: self)
        let result = await action(actor)
        return result
    }
    // throwing version
    nonisolated func runNonisolated<ResultType, ActorType: InitWithModelContainer>(
        action: @Sendable (_ actor: ActorType) async throws -> ResultType
    ) async throws -> ResultType {
        let actor = ActorType(modelContainer: self)
        let result = try await action(actor)
        return result
    }
}

protocol InitWithModelContainer {
    init(modelContainer: ModelContainer)
}

// MARK: - Usage: 

// Conform your @ModelActor to InitWithModelContainer (nothing needs to be implemented, the macro does it) 
@ModelActor
actor StudyStatsActor: InitWithModelContainer {
   func stats(forMonth:) …
}

// Calling runNonisolated (in this case, from a MainActor task):
.task {
  // closure must be sendable
  self.stats = await modelContext.container.runNonisolated { (actor: StudyStatsActor) in
    await actor.stats(forMonth: self.month, in:  calendar)
  }
}