Add GroupSendReport model

Sources/ElixxirDAppsSDK/Models/GroupSendReport.swift

+import Foundation
+
+public struct GroupSendReport: Equatable {
+  public init(
+    roundId: UInt64,
+    timestamp: Int64,
+    messageId: Data
+  ) {
+    self.roundId = roundId
+    self.timestamp = timestamp
+    self.messageId = messageId
+  }
+
+  public var roundId: UInt64
+  public var timestamp: Int64
+  public var messageId: Data
+}
+
+extension GroupSendReport: Codable {
+  enum CodingKeys: String, CodingKey {
+    case roundId = "RoundID"
+    case timestamp = "Timestamp"
+    case messageId = "MessageID"
+  }
+
+  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/GroupSendReportTests.swift

+import CustomDump
+import XCTest
+@testable import ElixxirDAppsSDK
+
+final class GroupSendReportTests: XCTestCase {
+  func testCoding() throws {
+    let roundId: UInt64 = 123
+    let timestamp: Int64 = 321
+    let messageIdB64 = "EB/70R5HYEw5htZ4Hg9ondrn3+cAc/lH2G0mjQMja3w="
+    let jsonString = """
+    {
+      "RoundID": \(roundId),
+      "Timestamp": \(timestamp),
+      "MessageID": "\(messageIdB64)"
+    }
+    """
+    let jsonData = jsonString.data(using: .utf8)!
+    let model = try GroupSendReport.decode(jsonData)
+
+    XCTAssertNoDifference(model, GroupSendReport(
+      roundId: roundId,
+      timestamp: timestamp,
+      messageId: Data(base64Encoded: messageIdB64)!
+    ))
+
+    let encodedModel = try model.encode()
+    let decodedModel = try GroupSendReport.decode(encodedModel)
+
+    XCTAssertNoDifference(decodedModel, model)
+  }
+}