Add InitializeBackup functor

Sources/ElixxirDAppsSDK/Functors/InitializeBackup.swift

+import Bindings
+import XCTestDynamicOverlay
+
+public struct InitializeBackup {
+  public var run: (Int, Int, String, UpdateBackupFunc) throws -> Backup
+
+  public func callAsFunction(
+    e2eId: Int,
+    udId: Int,
+    password: String,
+    callback: UpdateBackupFunc
+  ) throws -> Backup {
+    try run(e2eId, udId, password, callback)
+  }
+}
+
+extension InitializeBackup {
+  public static let live = InitializeBackup { e2eId, udId, password, callback in
+    var error: NSError?
+    let bindingsBackup = BindingsInitializeBackup(
+      e2eId,
+      udId,
+      password,
+      callback.makeBindingsUpdateBackupFunc(),
+      &error
+    )
+    if let error = error {
+      throw error
+    }
+    guard let bindingsBackup = bindingsBackup else {
+      fatalError("BindingsInitializeBackup returned `nil` without providing error")
+    }
+    return .live(bindingsBackup)
+  }
+}
+
+extension InitializeBackup {
+  public static let unimplemented = InitializeBackup(
+    run: XCTUnimplemented("\(Self.self)")
+  )
+}