feature: Add INVITE_CREATE and INVITE_DELETE events (#1491)

* Add invite events (create and delete)

* Removed unused using

* Fixing IInviteMetadata properties

* Add two new fields to the gateway event

* Better event summary and remarks

* Change how to assign to target variable

Co-Authored-By: Joe4evr <jii.geugten@gmail.com>

* Applying suggested changes to TargetUserType

* Renaming NotDefined to Undefined

* Fixing xml docs

* Changed the summary style format

Co-authored-by: Joe4evr <jii.geugten@gmail.com>

src/Discord.Net.WebSocket/API/Gateway/InviteCreateEvent.cs

@@ -0,0 +1,31 @@
+using Newtonsoft.Json;
+using System;
+
+namespace Discord.API.Gateway
+{
+    internal class InviteCreateEvent
+    {
+        [JsonProperty("channel_id")]
+        public ulong ChannelId { get; set; }
+        [JsonProperty("code")]
+        public string Code { get; set; }
+        [JsonProperty("created_at")]
+        public DateTimeOffset CreatedAt { get; set; }
+        [JsonProperty("guild_id")]
+        public Optional<ulong> GuildId { get; set; }
+        [JsonProperty("inviter")]
+        public Optional<User> Inviter { get; set; }
+        [JsonProperty("max_age")]
+        public int MaxAge { get; set; }
+        [JsonProperty("max_uses")]
+        public int MaxUses { get; set; }
+        [JsonProperty("target_user")]
+        public Optional<User> TargetUser { get; set; }
+        [JsonProperty("target_user_type")]
+        public Optional<TargetUserType> TargetUserType { get; set; }
+        [JsonProperty("temporary")]
+        public bool Temporary { get; set; }
+        [JsonProperty("uses")]
+        public int Uses { get; set; }
+    }
+}

src/Discord.Net.WebSocket/API/Gateway/InviteDeleteEvent.cs

@@ -0,0 +1,14 @@
+using Newtonsoft.Json;
+
+namespace Discord.API.Gateway
+{
+    internal class InviteDeleteEvent
+    {
+        [JsonProperty("channel_id")]
+        public ulong ChannelId { get; set; }
+        [JsonProperty("code")]
+        public string Code { get; set; }
+        [JsonProperty("guild_id")]
+        public Optional<ulong> GuildId { get; set; }
+    }
+}