Tidy up project structure, fix bug with edit logging (#47)

The project structure has been changed because the previous one had
everything in 1 folder. From this PR onwards, the following is true:
- The source code is stored in `src/`
- `*.resx` and `Messages.Designer.cs` is stored in `locale/`
- Documentation is stored on the wiki and in `docs/`
- Miscellaneous files, such as dotfiles, are stored in the root folder
of the repository

This PR additionally fixes an issue that would cause logs of edited
messages to not be syntax highlighted. This happened because the
responder of edited messages was changed to use the universal
`InBlockCode` extension method which did not support syntax highlighting
until this PR

This PR additionally changes CODEOWNERS to be more reliable. Previously,
it would be possible for some PRs to be unable to be approved because
the only person who can approve them is the same person who opened the
PR.

---------

Signed-off-by: Octol1ttle <l1ttleofficial@outlook.com>

src/Commands/RemindCommandGroup.cs

@@ -0,0 +1,75 @@
+using System.ComponentModel;
+using Boyfriend.Data;
+using Boyfriend.Services;
+using Remora.Commands.Attributes;
+using Remora.Commands.Groups;
+using Remora.Discord.API.Abstractions.Rest;
+using Remora.Discord.Commands.Contexts;
+using Remora.Discord.Commands.Feedback.Services;
+using Remora.Discord.Extensions.Embeds;
+using Remora.Discord.Extensions.Formatting;
+using Remora.Results;
+
+// ReSharper disable ClassNeverInstantiated.Global
+// ReSharper disable UnusedMember.Global
+
+namespace Boyfriend.Commands;
+
+/// <summary>
+///     Handles the command to manage reminders: /remind
+/// </summary>
+public class RemindCommandGroup : CommandGroup {
+    private readonly ICommandContext     _context;
+    private readonly GuildDataService    _dataService;
+    private readonly FeedbackService     _feedbackService;
+    private readonly IDiscordRestUserAPI _userApi;
+
+    public RemindCommandGroup(
+        ICommandContext     context, GuildDataService dataService, FeedbackService feedbackService,
+        IDiscordRestUserAPI userApi) {
+        _context = context;
+        _dataService = dataService;
+        _feedbackService = feedbackService;
+        _userApi = userApi;
+    }
+
+    /// <summary>
+    ///     A slash command that schedules a reminder with the specified text.
+    /// </summary>
+    /// <param name="in">The period of time which must pass before the reminder will be sent.</param>
+    /// <param name="message">The text of the reminder.</param>
+    /// <returns>A feedback sending result which may or may not have succeeded.</returns>
+    [Command("remind")]
+    [Description("Create a reminder")]
+    public async Task<Result> AddReminderAsync(
+        [Description("After what period of time mention the reminder")]
+        TimeSpan @in,
+        [Description("Reminder message")] string message) {
+        if (!_context.TryGetContextIDs(out var guildId, out var channelId, out var userId))
+            return Result.FromError(
+                new ArgumentNullError(nameof(_context), "Unable to retrieve necessary IDs from command context"));
+
+        var userResult = await _userApi.GetUserAsync(userId.Value, CancellationToken);
+        if (!userResult.IsDefined(out var user))
+            return Result.FromError(userResult);
+
+        var remindAt = DateTimeOffset.UtcNow.Add(@in);
+
+        (await _dataService.GetMemberData(guildId.Value, userId.Value, CancellationToken)).Reminders.Add(
+            new Reminder {
+                RemindAt = remindAt,
+                Channel = channelId.Value,
+                Text = message
+            });
+
+        var embed = new EmbedBuilder().WithSmallTitle(string.Format(Messages.ReminderCreated, user.GetTag()), user)
+            .WithDescription(string.Format(Messages.DescriptionReminderCreated, Markdown.Timestamp(remindAt)))
+            .WithColour(ColorsList.Green)
+            .Build();
+
+        if (!embed.IsDefined(out var built))
+            return Result.FromError(embed);
+
+        return (Result)await _feedbackService.SendContextualEmbedAsync(built, ct: CancellationToken);
+    }
+}