Conversion of HockeyApp to AppCenter for crash reporting (#810)

* Conversion of HockeyApp to AppCenter for crash reporting

* Corrected older-style nuget package definition

src/iOS.Core/Utilities/AppCenterHelper.cs

@@ -0,0 +1,56 @@
+using Bit.Core.Abstractions;
+using System.Threading.Tasks;
+using Microsoft.AppCenter;
+using Microsoft.AppCenter.Crashes;
+using Newtonsoft.Json;
+
+namespace Bit.iOS.Core.Utilities
+{
+    public class AppCenterHelper
+    {
+        private const string AppSecret = "51f96ae5-68ba-45f6-99a1-8ad9f63046c3";
+
+        private readonly IAppIdService _appIdService;
+        private readonly IUserService _userService;
+
+        private string _userId;
+        private string _appId;
+
+        public AppCenterHelper(
+            IAppIdService appIdService,
+            IUserService userService)
+        {
+            _appIdService = appIdService;
+            _userService = userService;
+        }
+
+        public async Task InitAsync()
+        {
+            _userId = await _userService.GetUserIdAsync();
+            _appId = await _appIdService.GetAppIdAsync();
+            
+            AppCenter.Start(AppSecret, typeof(Crashes));
+            AppCenter.SetUserId(_userId);
+            
+            Crashes.GetErrorAttachments = (ErrorReport report) =>
+            {
+                return new ErrorAttachmentLog[]
+                {
+                    ErrorAttachmentLog.AttachmentWithText(Description, "crshdesc.txt"),
+                };
+            };
+        }
+
+        public string Description
+        {
+            get
+            {
+                return JsonConvert.SerializeObject(new
+                {
+                    AppId = _appId,
+                    UserId = _userId
+                }, Formatting.Indented);
+            }
+        }
+    }
+}