Update the Vkontakte provider to extract the email address from the token response

Author: Семёновых Алексей

src/AspNet.Security.OAuth.Vkontakte/VkontakteAuthenticationHandler.cs

@@ -49,7 +49,13 @@ protected override async Task<AuthenticationTicket> CreateTicketAsync([NotNull]
             var payload = JObject.Parse(await response.Content.ReadAsStringAsync());
             var user = (JObject) payload["response"][0];
 
+            if (tokens.Response["email"] != null)
+            {
+                user.Add("email", tokens.Response["email"]);
+            }
+
             identity.AddOptionalClaim(ClaimTypes.NameIdentifier, VkontakteAuthenticationHelper.GetId(user), Options.ClaimsIssuer)
+                    .AddOptionalClaim(ClaimTypes.Email, VkontakteAuthenticationHelper.GetEmail(user), Options.ClaimsIssuer)
                     .AddOptionalClaim(ClaimTypes.GivenName, VkontakteAuthenticationHelper.GetFirstName(user), Options.ClaimsIssuer)
                     .AddOptionalClaim(ClaimTypes.Surname, VkontakteAuthenticationHelper.GetLastName(user), Options.ClaimsIssuer)
                     .AddOptionalClaim(ClaimTypes.Hash, VkontakteAuthenticationHelper.GetHash(user), Options.ClaimsIssuer)

src/AspNet.Security.OAuth.Vkontakte/VkontakteAuthenticationHelper.cs

@@ -42,6 +42,19 @@ public static string GetHash([NotNull] JObject user)
             return user.Value<string>("hash");
         }
 
+        /// <summary>
+        /// Gets the email address associated with the logged in user.
+        /// </summary>
+        public static string GetEmail([NotNull] JObject user)
+        {
+            if (user == null)
+            {
+                throw new ArgumentNullException(nameof(user));
+            }
+
+            return user.Value<string>("email");
+        }
+
         /// <summary>
         /// Gets the first name associated with the logged in user.
         /// </summary>