add `AppliedTags` property

src/Discord.Net.Core/Entities/Channels/IThreadChannel.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Threading.Tasks;
 
 namespace Discord
@@ -56,6 +57,14 @@ namespace Discord
         /// </remarks>
         bool? IsInvitable { get; }
 
+        /// <summary>
+        ///     Gets ids of tags applied to a forum thread
+        /// </summary>
+        /// <remarks>
+        ///     This property is only available on forum threads.
+        /// </remarks>
+        IReadOnlyCollection<ulong> AppliedTags { get; }
+
         /// <summary>
         ///     Gets when the thread was created.
         /// </summary>

src/Discord.Net.Core/Entities/Channels/TextChannelProperties.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 
 namespace Discord
 {
@@ -53,6 +54,11 @@ namespace Discord
         ///     Gets or sets the auto archive duration.
         /// </summary>
         public Optional<ThreadArchiveDuration> AutoArchiveDuration { get; set; }
-        
+
+        /// <summary>
+        /// Gets or sets the tags applied to a forum thread
+        /// </summary>
+        public Optional<IEnumerable<ulong>> AppliedTags { get; set; }
+
     }
 }

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

@@ -70,7 +70,10 @@ namespace Discord.API
         //ForumChannel
         [JsonProperty("available_tags")]
         public Optional<ForumTags[]> ForumTags { get; set; }
-        
+
+        [JsonProperty("applied_tags")]
+        public Optional<ulong[]> AppliedTags { get; set; }
+
         [JsonProperty("default_auto_archive_duration")]
         public Optional<ThreadArchiveDuration> AutoArchiveDuration { get; set; }
     }

src/Discord.Net.Rest/API/Rest/ModifyThreadParams.cs

@@ -1,4 +1,5 @@
 using Newtonsoft.Json;
+using System.Collections.Generic;
 
 namespace Discord.API.Rest
 {
@@ -18,5 +19,8 @@ namespace Discord.API.Rest
 
         [JsonProperty("rate_limit_per_user")]
         public Optional<int> Slowmode { get; set; }
+
+        [JsonProperty("applied_tags")]
+        public Optional<IEnumerable<ulong>> AppliedTags { get; set; }
     }
 }

src/Discord.Net.Rest/Entities/Channels/RestThreadChannel.cs

@@ -37,6 +37,9 @@ namespace Discord.Rest
         /// <inheritdoc/>
         public bool? IsInvitable { get; private set; }
 
+        /// <inheritdoc/>
+        public IReadOnlyCollection<ulong> AppliedTags { get; private set; }
+
         /// <inheritdoc cref="IThreadChannel.CreatedAt"/>
         public override DateTimeOffset CreatedAt { get; }
 
@@ -77,6 +80,8 @@ namespace Discord.Rest
             MessageCount = model.MessageCount.GetValueOrDefault(0);
             Type = (ThreadType)model.Type;
             ParentChannelId = model.CategoryId.Value;
+
+            AppliedTags = model.AppliedTags.GetValueOrDefault(Array.Empty<ulong>());
         }
 
         /// <summary>

src/Discord.Net.Rest/Entities/Channels/ThreadHelper.cs

@@ -57,7 +57,8 @@ namespace Discord.Rest
                 Archived = args.Archived,
                 AutoArchiveDuration = args.AutoArchiveDuration,
                 Locked = args.Locked,
-                Slowmode = args.SlowModeInterval
+                Slowmode = args.SlowModeInterval,
+                AppliedTags = args.AppliedTags
             };
             return await client.ApiClient.ModifyThreadAsync(channel.Id, apiArgs, options).ConfigureAwait(false);
         }

src/Discord.Net.WebSocket/Entities/Channels/SocketThreadChannel.cs

@@ -89,6 +89,9 @@ namespace Discord.WebSocket
         /// <inheritdoc/>
         public bool? IsInvitable { get; private set; }
 
+        /// <inheritdoc/>
+        public IReadOnlyCollection<ulong> AppliedTags { get; private set; }
+
         /// <inheritdoc cref="IThreadChannel.CreatedAt"/>
         public override DateTimeOffset CreatedAt { get; }
 
@@ -149,6 +152,8 @@ namespace Discord.WebSocket
             }
 
             HasJoined = model.ThreadMember.IsSpecified;
+
+            AppliedTags = model.AppliedTags.GetValueOrDefault(Array.Empty<ulong>());
         }
 
         internal IReadOnlyCollection<SocketThreadUser> RemoveUsers(ulong[] users)