Add Progress model

Sources/ElixxirDAppsSDK/Models/Progress.swift

+import Foundation
+
+public struct Progress: Equatable {
+  public init(
+    completed: Bool,
+    transmitted: Int,
+    total: Int
+  ) {
+    self.completed = completed
+    self.transmitted = transmitted
+    self.total = total
+  }
+
+  public var completed: Bool
+  public var transmitted: Int
+  public var total: Int
+  // TODO: add error
+  // public var error: ???
+}
+import Bindings
+
+extension Progress: Codable {
+  enum CodingKeys: String, CodingKey {
+    case completed = "Completed"
+    case transmitted = "Transmitted"
+    case total = "Total"
+    // TODO: add error
+    // case error = "Err"
+  }
+
+  public static func decode(_ data: Data) throws -> Self {
+    try JSONDecoder().decode(Self.self, from: data)
+  }
+
+  public func encode() throws -> Data {
+    try JSONEncoder().encode(self)
+  }
+}

Tests/ElixxirDAppsSDKTests/Models/ProgressTests.swift

+import CustomDump
+import XCTest
+@testable import ElixxirDAppsSDK
+
+final class ProgressTests: XCTestCase {
+  func testCoding() throws {
+    let completed = false
+    let transmitted: Int = 128
+    let total: Int = 2048
+    let jsonString = """
+    {
+      "Completed": \(completed),
+      "Transmitted": \(transmitted),
+      "Total": \(total),
+      "Err": null
+    }
+    """
+    let jsonData = jsonString.data(using: .utf8)!
+    let progress = try Progress.decode(jsonData)
+
+    XCTAssertNoDifference(progress, Progress(
+      completed: completed,
+      transmitted: transmitted,
+      total: total
+    ))
+
+    let encodedProgress = try progress.encode()
+    let decodedProgress = try Progress.decode(encodedProgress)
+
+    XCTAssertNoDifference(decodedProgress, progress)
+  }
+}