Fix: Integration model from GuildIntegration and added INTEGRATION gateway events (#2168)

* fix integration models; add integration events

* fix description on IGUILD for integration

* fix typo in integration documentation

* fix documentation in connection visibility

* removed public identitiers from app and connection

* Removed REST endpoints that are not part of the API.

* Added documentation for rest integrations

* added optional types

* Fixed rest interaction field with not being IsSpecified

src/Discord.Net.Rest/ClientHelper.cs

@@ -49,7 +49,7 @@ namespace Discord.Rest
         public static async Task<IReadOnlyCollection<RestConnection>> GetConnectionsAsync(BaseDiscordClient client, RequestOptions options)
         {
             var models = await client.ApiClient.GetMyConnectionsAsync(options).ConfigureAwait(false);
-            return models.Select(RestConnection.Create).ToImmutableArray();
+            return models.Select(model => RestConnection.Create(client, model)).ToImmutableArray();
         }
 
         public static async Task<RestInviteMetadata> GetInviteAsync(BaseDiscordClient client,