Add warn command (#3)

In the format:
warn <id> [reason]
or
warn <user> [reason]

Hammer/CommandModules/Staff/StaffModule.Warn.cs

@@ -0,0 +1,60 @@
+using System.Threading.Tasks;
+using BrackeysBot.API.Extensions;
+using DisCatSharp;
+using DisCatSharp.CommandsNext;
+using DisCatSharp.CommandsNext.Attributes;
+using DisCatSharp.Entities;
+using Hammer.Attributes;
+using Hammer.Data;
+using Hammer.Extensions;
+using Hammer.Resources;
+using Humanizer;
+using SmartFormat;
+using PermissionLevel = Hammer.Data.PermissionLevel;
+
+namespace Hammer.CommandModules.Staff;
+
+internal sealed partial class StaffModule
+{
+    [Command("warn")]
+    [Description("Issues a warning to a user.")]
+    [RequirePermissionLevel(PermissionLevel.Moderator)]
+    public async Task WarnCommandAsync(CommandContext context, [Description("The ID of the user to warn.")] ulong userId,
+        [Description("The reason for the warning")] [RemainingText]
+        string? reason = null)
+    {
+        DiscordUser user = await context.Client.GetUserAsync(userId);
+
+        if (user is null)
+        {
+            var embed = new DiscordEmbedBuilder();
+            embed.WithColor(0xFF0000);
+            embed.WithTitle(EmbedTitles.NoSuchUser);
+            embed.WithDescription(EmbedMessages.NoSuchUser.FormatSmart(new {id = userId}));
+            await context.RespondAsync(embed);
+            return;
+        }
+
+        await WarnCommandAsync(context, user, reason);
+    }
+
+    [Command("warn")]
+    [Description("Issues a warning to a user.")]
+    [RequirePermissionLevel(PermissionLevel.Moderator)]
+    public async Task WarnCommandAsync(CommandContext context, [Description("The user to warn.")] DiscordUser user,
+        [Description("The reason for the warning")] [RemainingText]
+        string? reason = null)
+    {
+        await context.AcknowledgeAsync();
+
+        Infraction infraction = await _infractionService.WarnAsync(user, context.Member, reason);
+        var embed = new DiscordEmbedBuilder();
+        embed.WithColor(0xFF0000);
+        embed.WithTitle(infraction.Type.Humanize());
+        embed.WithDescription(infraction.Reason.WithWhiteSpaceAlternative(Formatter.Italic("<no reason specified>")));
+        embed.WithAuthor(user);
+        embed.WithFooter($"Infraction #{infraction.Id} \u2022 User #{user.Id}");
+
+        await context.RespondAsync(embed);
+    }
+}