feature: support guild subscription opt-out (#1386)

Author: k-boyle

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

@@ -15,5 +15,7 @@ internal class IdentifyParams
         public int LargeThreshold { get; set; }
         [JsonProperty("shard")]
         public Optional<int[]> ShardingParams { get; set; }
+        [JsonProperty("guild_subscriptions")]
+        public Optional<bool> GuildSubscriptions { get; set; }
     }
 }

src/Discord.Net.WebSocket/DiscordSocketApiClient.cs

@@ -215,7 +215,7 @@ private async Task SendGatewayInternalAsync(GatewayOpCode opCode, object payload
             await _sentGatewayMessageEvent.InvokeAsync(opCode).ConfigureAwait(false);
         }
 
-        public async Task SendIdentifyAsync(int largeThreshold = 100, int shardID = 0, int totalShards = 1, RequestOptions options = null)
+        public async Task SendIdentifyAsync(int largeThreshold = 100, int shardID = 0, int totalShards = 1, bool guildSubscriptions = true, RequestOptions options = null)
         {
             options = RequestOptions.CreateOrClone(options);
             var props = new Dictionary<string, string>
@@ -226,7 +226,8 @@ public async Task SendIdentifyAsync(int largeThreshold = 100, int shardID = 0, i
             {
                 Token = AuthToken,
                 Properties = props,
-                LargeThreshold = largeThreshold
+                LargeThreshold = largeThreshold,
+                GuildSubscriptions = guildSubscriptions
             };
             if (totalShards > 1)
                 msg.ShardingParams = new int[] { shardID, totalShards };

src/Discord.Net.WebSocket/DiscordSocketClient.cs

@@ -43,6 +43,7 @@ public partial class DiscordSocketClient : BaseSocketClient, IDiscordClient
         private DateTimeOffset? _statusSince;
         private RestApplication _applicationInfo;
         private bool _isDisposed;
+        private bool _guildSubscriptions;
 
         /// <summary>
         ///     Provides access to a REST-only client with a shared state from this client.
@@ -135,6 +136,7 @@ private DiscordSocketClient(DiscordSocketConfig config, API.DiscordSocketApiClie
             State = new ClientState(0, 0);
             Rest = new DiscordSocketRestClient(config, ApiClient);
             _heartbeatTimes = new ConcurrentQueue<long>();
+            _guildSubscriptions = config.GuildSubscriptions;
 
             _stateLock = new SemaphoreSlim(1, 1);
             _gatewayLogger = LogManager.CreateLogger(ShardId == 0 && TotalShards == 1 ? "Gateway" : $"Shard #{ShardId}");
@@ -240,7 +242,7 @@ private async Task OnConnectingAsync()
                 else
                 {
                     await _gatewayLogger.DebugAsync("Identifying").ConfigureAwait(false);
-                    await ApiClient.SendIdentifyAsync(shardID: ShardId, totalShards: TotalShards).ConfigureAwait(false);
+                    await ApiClient.SendIdentifyAsync(shardID: ShardId, totalShards: TotalShards, guildSubscriptions: _guildSubscriptions).ConfigureAwait(false);
                 }
 
                 //Wait for READY

src/Discord.Net.WebSocket/DiscordSocketConfig.cs

@@ -77,7 +77,7 @@ public class DiscordSocketConfig : DiscordRestConfig
         ///     <para>
         ///         By default, the Discord gateway will only send offline members if a guild has less than a certain number
         ///         of members (determined by <see cref="LargeThreshold"/> in this library). This behaviour is why
-        ///         sometimes a user may be missing from the WebSocket cache for collections such as 
+        ///         sometimes a user may be missing from the WebSocket cache for collections such as
         ///         <see cref="Discord.WebSocket.SocketGuild.Users"/>.
         ///     </para>
         ///     <para>
@@ -86,7 +86,7 @@ public class DiscordSocketConfig : DiscordRestConfig
         ///         downloaded to the WebSocket cache.
         ///     </para>
         ///     <para>
-        ///         For more information, please see 
+        ///         For more information, please see
         ///         <see href="https://discordapp.com/developers/docs/topics/gateway#request-guild-members">Request Guild Members</see>
         ///         on the official Discord API documentation.
         ///     </para>
@@ -95,7 +95,7 @@ public class DiscordSocketConfig : DiscordRestConfig
         ///         traffic. If you are using the command system, the default user TypeReader may fail to find the user
         ///         due to this issue. This may be resolved at v3 of the library. Until then, you may want to consider
         ///         overriding the TypeReader and use
-        ///         <see cref="DiscordRestClient.GetUserAsync(System.UInt64,Discord.RequestOptions)"/> 
+        ///         <see cref="DiscordRestClient.GetUserAsync(System.UInt64,Discord.RequestOptions)"/>
         ///         or <see cref="DiscordRestClient.GetGuildUserAsync"/>
         ///         as a backup.
         ///     </note>
@@ -119,6 +119,11 @@ public class DiscordSocketConfig : DiscordRestConfig
         /// </summary>
         public bool? ExclusiveBulkDelete { get; set; } = null;
 
+        /// <summary>
+        ///     Gets or sets enabling dispatching of guild subscription events e.g. presence and typing events.
+        /// </summary>
+        public bool GuildSubscriptions { get; set; } = true;
+
         /// <summary>
         ///     Initializes a default configuration.
         /// </summary>