Apply official naming guidelines to Octobot (#306)

1. The root namespace was changed from `Octobot` to
`TeamOctolings.Octobot`:
> DO prefix namespace names with a company name to prevent namespaces
from different companies from having the same name.
2. `Octobot.cs` was renamed to `Program.cs`:
> DO NOT use the same name for a namespace and a type in that namespace.
3. `IOption`, `Option` were renamed to `IGuildOption` and `GuildOption`
respectively:
> DO NOT introduce generic type names such as Element, Node, Log, and
Message.
4. `Utility` was moved out of the `Services` namespace. It didn't belong
there anyway
5. `Program` static fields were moved to `Utility`
6. Localisation files were moved back to the project source files. Looks
like this fixed `Message.Designer.cs` code generation

---------

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

TeamOctolings.Octobot/Responders/MessageEditedResponder.cs

@@ -0,0 +1,109 @@
+using System.Text;
+using DiffPlex.DiffBuilder;
+using JetBrains.Annotations;
+using Remora.Discord.API.Abstractions.Gateway.Events;
+using Remora.Discord.API.Abstractions.Objects;
+using Remora.Discord.API.Abstractions.Rest;
+using Remora.Discord.Caching;
+using Remora.Discord.Caching.Services;
+using Remora.Discord.Extensions.Embeds;
+using Remora.Discord.Gateway.Responders;
+using Remora.Results;
+using TeamOctolings.Octobot.Data;
+using TeamOctolings.Octobot.Extensions;
+using TeamOctolings.Octobot.Services;
+
+namespace TeamOctolings.Octobot.Responders;
+
+/// <summary>
+///     Handles logging the difference between an edited message's old and new content
+///     to a guild's <see cref="GuildSettings.PrivateFeedbackChannel" /> if one is set.
+/// </summary>
+[UsedImplicitly]
+public class MessageEditedResponder : IResponder<IMessageUpdate>
+{
+    private readonly CacheService _cacheService;
+    private readonly IDiscordRestChannelAPI _channelApi;
+    private readonly GuildDataService _guildData;
+
+    public MessageEditedResponder(
+        CacheService cacheService, IDiscordRestChannelAPI channelApi, GuildDataService guildData)
+    {
+        _cacheService = cacheService;
+        _channelApi = channelApi;
+        _guildData = guildData;
+    }
+
+    public async Task<Result> RespondAsync(IMessageUpdate gatewayEvent, CancellationToken ct = default)
+    {
+        if (!gatewayEvent.ID.IsDefined(out var messageId))
+        {
+            return new ArgumentNullError(nameof(gatewayEvent.ID));
+        }
+
+        if (!gatewayEvent.ChannelID.IsDefined(out var channelId))
+        {
+            return new ArgumentNullError(nameof(gatewayEvent.ChannelID));
+        }
+
+        if (!gatewayEvent.GuildID.IsDefined(out var guildId)
+            || !gatewayEvent.Author.IsDefined(out var author)
+            || !gatewayEvent.EditedTimestamp.IsDefined(out var timestamp)
+            || !gatewayEvent.Content.IsDefined(out var newContent))
+        {
+            return Result.Success;
+        }
+
+        var cfg = await _guildData.GetSettings(guildId, ct);
+        if (author.IsBot.OrDefault(false) || GuildSettings.PrivateFeedbackChannel.Get(cfg).Empty())
+        {
+            return Result.Success;
+        }
+
+        var cacheKey = new KeyHelpers.MessageCacheKey(channelId, messageId);
+        var messageResult = await _cacheService.TryGetValueAsync<IMessage>(
+            cacheKey, ct);
+        if (!messageResult.IsDefined(out var message))
+        {
+            _ = _channelApi.GetChannelMessageAsync(channelId, messageId, ct);
+            return Result.Success;
+        }
+
+        if (message.Content == newContent)
+        {
+            return Result.Success;
+        }
+
+        // Custom event responders are called earlier than responders responsible for message caching
+        // This means that subsequent edit logs may contain the wrong content
+        // We can work around this by evicting the message from the cache
+        await _cacheService.EvictAsync<IMessage>(cacheKey, ct);
+        // However, since we evicted the message, subsequent edits won't have a cached instance to work with
+        // Getting the message will put it back in the cache, resolving all issues
+        // We don't need to await this since the result is not needed
+        // NOTE: Because this is not awaited, there may be a race condition depending on how fast clients are able to edit their messages
+        // NOTE: Awaiting this might not even solve this if the same responder is called asynchronously
+        _ = _channelApi.GetChannelMessageAsync(channelId, messageId, ct);
+
+        var diff = InlineDiffBuilder.Diff(message.Content, newContent);
+
+        Messages.Culture = GuildSettings.Language.Get(cfg);
+
+        var builder = new StringBuilder()
+            .AppendLine(diff.AsMarkdown())
+            .AppendLine(string.Format(Messages.DescriptionActionJumpToMessage,
+                $"https://discord.com/channels/{guildId}/{channelId}/{messageId}")
+            );
+
+        var embed = new EmbedBuilder()
+            .WithSmallTitle(string.Format(Messages.CachedMessageEdited, message.Author.GetTag()), message.Author)
+            .WithDescription(builder.ToString())
+            .WithTimestamp(timestamp.Value)
+            .WithColour(ColorsList.Yellow)
+            .Build();
+
+        return await _channelApi.CreateMessageWithEmbedResultAsync(
+            GuildSettings.PrivateFeedbackChannel.Get(cfg), embedResult: embed,
+            allowedMentions: Utility.NoMentions, ct: ct);
+    }
+}