[Feature] Generic autocomplete (#2935)

src/Discord.Net.Interactions/Attributes/AutocompleteAttribute.cs

@@ -1,7 +1,7 @@
 using System;
 
-namespace Discord.Interactions
-{
+namespace Discord.Interactions;
+
 /// <summary>
 ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/>.
 /// </summary>
@@ -27,10 +27,12 @@ namespace Discord.Interactions
 
         AutocompleteHandlerType = autocompleteHandlerType;
     }
+}
 
 /// <summary>
-        ///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/> without specifying a <see cref="AutocompleteHandler"/>.
+///     Set the <see cref="ApplicationCommandOptionProperties.IsAutocomplete"/> to <see langword="true"/>.
 /// </summary>
-        public AutocompleteAttribute() { }
-    }
-}
+/// <typeparam name="T">Type of the <see cref="AutocompleteHandler"/> that will be used to handle Autocomplete interactions targeting the parameter.</typeparam>
+[AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = true)]
+public class AutocompleteAttribute<T>() : AutocompleteAttribute(typeof(T))
+    where T : class, IAutocompleteHandler;