feature: Implemented Message Reference Property (#1413)

* Added support for Message References

* Removed unused usings, added debugger display, updated ToString override

* Changed snowflakes to be wrapped in an optional instead of a nullable.

src/Discord.Net.Rest/API/Common/Message.cs

@@ -50,6 +50,8 @@ namespace Discord.API
         // sent with Rich Presence-related chat embeds
         [JsonProperty("application")]
         public Optional<MessageApplication> Application { get; set; }
+        [JsonProperty("message_reference")]
+        public Optional<MessageReference> Reference { get; set; }
         [JsonProperty("flags")]
         public Optional<MessageFlags> Flags { get; set; }
     }

src/Discord.Net.Rest/API/Common/MessageReference.cs

@@ -0,0 +1,16 @@
+using Newtonsoft.Json;
+
+namespace Discord.API
+{
+    internal class MessageReference
+    {
+        [JsonProperty("message_id")]
+        public Optional<ulong> MessageId { get; set; }
+
+        [JsonProperty("channel_id")]
+        public ulong ChannelId { get; set; }
+
+        [JsonProperty("guild_id")]
+        public Optional<ulong> GuildId { get; set; }
+    }
+}

src/Discord.Net.Rest/Entities/Messages/RestMessage.cs

@@ -62,6 +62,8 @@ namespace Discord.Rest
         public MessageActivity Activity { get; private set; }
         /// <inheritdoc />
         public MessageApplication Application { get; private set; }
+        /// <inheritdoc />
+        public MessageReference Reference { get; private set; }
 
         internal RestMessage(BaseDiscordClient discord, ulong id, IMessageChannel channel, IUser author, MessageSource source)
             : base(discord, id)
@@ -108,6 +110,17 @@ namespace Discord.Rest
                 };
             }
 
+            if(model.Reference.IsSpecified)
+            {
+                // Creates a new Reference from the API model
+                Reference = new MessageReference
+                {
+                    GuildId = model.Reference.Value.GuildId,
+                    ChannelId = model.Reference.Value.ChannelId,
+                    MessageId = model.Reference.Value.MessageId
+                };
+            }
+
             if (model.Reactions.IsSpecified)
             {
                 var value = model.Reactions.Value;