Allow preconditions to be used multiple times (for use with groups)

src/Discord.Net.Commands/Attributes/Preconditions/RequireContextAttribute.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Threading.Tasks;
 using Microsoft.Extensions.DependencyInjection;
 
@@ -15,7 +15,7 @@ namespace Discord.Commands
     /// <summary>
     /// Require that the command be invoked in a specified context.
     /// </summary>
-    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
     public class RequireContextAttribute : PreconditionAttribute
     {
         public ContextType Contexts { get; }

src/Discord.Net.Commands/Attributes/Preconditions/RequireNsfwAttribute.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Threading.Tasks;
 
 namespace Discord.Commands
@@ -6,7 +6,7 @@ namespace Discord.Commands
     /// <summary>
     /// Require that the command is invoked in a channel marked NSFW
     /// </summary>
-    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
     public class RequireNsfwAttribute : PreconditionAttribute
     {
         public override Task<PreconditionResult> CheckPermissionsAsync(ICommandContext context, CommandInfo command, IServiceProvider services)

src/Discord.Net.Commands/Attributes/Preconditions/RequireOwnerAttribute.cs

@@ -1,7 +1,6 @@
-#pragma warning disable CS0618
+#pragma warning disable CS0618
 using System;
 using System.Threading.Tasks;
-using Microsoft.Extensions.DependencyInjection;
 
 namespace Discord.Commands
 {
@@ -9,7 +8,7 @@ namespace Discord.Commands
     /// Require that the command is invoked by the owner of the bot.
     /// </summary>
     /// <remarks>This precondition will only work if the bot is a bot account.</remarks>
-    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
+    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = true, Inherited = true)]
     public class RequireOwnerAttribute : PreconditionAttribute
     {
         public override async Task<PreconditionResult> CheckPermissionsAsync(ICommandContext context, CommandInfo command, IServiceProvider services)