Add BroadcastReport model

Sources/ElixxirDAppsSDK/Models/BroadcastReport.swift

+import Foundation
+
+public struct BroadcastReport: Equatable {
+  public init(
+    roundId: Int,
+    ephId: [Int]
+  ) {
+    self.roundId = roundId
+    self.ephId = ephId
+  }
+
+  public var roundId: Int
+  public var ephId: [Int]
+}
+
+extension BroadcastReport: Codable {
+  enum CodingKeys: String, CodingKey {
+    case roundId = "RoundID"
+    case ephId = "EphID"
+  }
+
+  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/BroadcastReportTests.swift

+import CustomDump
+import XCTest
+@testable import ElixxirDAppsSDK
+
+final class BroadcastReportTests: XCTestCase {
+  func testCoding() throws {
+    let roundId: Int = 42
+    let ephId: [Int] = [0, 0, 0, 0, 0, 0, 24, 61]
+    let jsonString = """
+    {
+      "RoundID": \(roundId),
+      "EphID": [\(ephId.map { "\($0)" }.joined(separator: ", "))]
+    }
+    """
+    let jsonData = jsonString.data(using: .utf8)!
+    let report = try BroadcastReport.decode(jsonData)
+
+    XCTAssertNoDifference(report, BroadcastReport(
+      roundId: roundId,
+      ephId: ephId
+    ))
+
+    let encodedReport = try report.encode()
+    let decodedReport = try BroadcastReport.decode(encodedReport)
+
+    XCTAssertNoDifference(decodedReport, report)
+  }
+}