Messenger - backup

• Add functions to Messenger:
  • registerBackupCallback
  • isBackupRunning
  • startBackup
  • resumeBackup
  • stopBackup
  • backupParams
• Update docs
• Prevent backups without params

Sources/XXMessengerClient/Messenger/Functions/MessengerBackupParams.swift

+import Bindings
+import XCTestDynamicOverlay
+
+public struct MessengerBackupParams {
+  public enum Error: Swift.Error, Equatable {
+    case notRunning
+  }
+
+  public var run: (BackupParams) throws -> Void
+
+  public func callAsFunction(_ params: BackupParams) throws {
+    try run(params)
+  }
+}
+
+extension MessengerBackupParams {
+  public static func live(_ env: MessengerEnvironment) -> MessengerBackupParams {
+    MessengerBackupParams { params in
+      guard let backup = env.backup(), backup.isRunning() else {
+        throw Error.notRunning
+      }
+      let paramsData = try params.encode()
+      let paramsString = String(data: paramsData, encoding: .utf8)!
+      backup.addJSON(paramsString)
+    }
+  }
+}
+
+extension MessengerBackupParams {
+  public static let unimplemented = MessengerBackupParams(
+    run: XCTUnimplemented("\(Self.self)")
+  )
+}