Add GroupReport model

Sources/ElixxirDAppsSDK/Models/GroupReport.swift

+import Foundation
+
+public struct GroupReport: Equatable {
+  public init(
+    id: Data,
+    rounds: [Int],
+    status: Int
+  ) {
+    self.id = id
+    self.rounds = rounds
+    self.status = status
+  }
+
+  public var id: Data
+  public var rounds: [Int]
+  public var status: Int
+}
+
+extension GroupReport: Codable {
+  enum CodingKeys: String, CodingKey {
+    case id = "Id"
+    case rounds = "Rounds"
+    case status = "Status"
+  }
+
+  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/GroupReportTests.swift

+import CustomDump
+import XCTest
+@testable import ElixxirDAppsSDK
+
+final class GroupReportTests: XCTestCase {
+  func testCoding() throws {
+    let idB64 = "EB/70R5HYEw5htZ4Hg9ondrn3+cAc/lH2G0mjQMja3w="
+    let rounds: [Int] = [1, 5, 9]
+    let status: Int = 123
+    let jsonString = """
+    {
+      "Id": "\(idB64)",
+      "Rounds": [\(rounds.map { "\($0)" }.joined(separator: ", "))],
+      "Status": \(status)
+    }
+    """
+    let jsonData = jsonString.data(using: .utf8)!
+    let model = try GroupReport.decode(jsonData)
+
+    XCTAssertNoDifference(model, GroupReport(
+      id: Data(base64Encoded: idB64)!,
+      rounds: rounds,
+      status: status
+    ))
+
+    let encodedModel = try model.encode()
+    let decodedModel = try GroupReport.decode(encodedModel)
+
+    XCTAssertNoDifference(decodedModel, model)
+  }
+}