feat(discord): enable session join leave buttons

Move neutral join/leave handlers into GmRelay.Shared so Telegram and Discord share capacity, waitlist, duplicate-click, and schedule-update behavior.

Add Discord component routing for join_session and leave_session buttons with deferred ephemeral replies and serialized schedule message updates.

Bump version to 2.5.0 and update Discord docs.

Refs #29

src/GmRelay.DiscordBot/Features/Sessions/DiscordSessionInteractionMapper.cs

@@ -0,0 +1,64 @@
+using GmRelay.Shared.Features.Sessions.CreateSession;
+using GmRelay.Shared.Platform;
+
+namespace GmRelay.DiscordBot.Features.Sessions;
+
+public sealed record DiscordSessionInteractionInput(
+    Guid SessionId,
+    string InteractionId,
+    string GuildId,
+    string ChannelId,
+    string MessageId,
+    ulong UserId,
+    string Username,
+    string? DisplayName);
+
+public static class DiscordSessionInteractionMapper
+{
+    public static bool TryParseCustomId(string customId, string expectedAction, out Guid sessionId)
+    {
+        sessionId = default;
+
+        var parts = customId.Split(':', 2);
+        return parts.Length == 2
+            && string.Equals(parts[0], expectedAction, StringComparison.Ordinal)
+            && Guid.TryParse(parts[1], out sessionId);
+    }
+
+    public static JoinSessionCommand CreateJoinCommand(DiscordSessionInteractionInput input) =>
+        new(
+            SessionId: input.SessionId,
+            User: CreateUser(input),
+            InteractionId: input.InteractionId,
+            Group: CreateGroup(input),
+            ScheduleMessage: CreateMessageRef(input));
+
+    public static LeaveSessionCommand CreateLeaveCommand(DiscordSessionInteractionInput input) =>
+        new(
+            SessionId: input.SessionId,
+            User: CreateUser(input),
+            InteractionId: input.InteractionId,
+            Group: CreateGroup(input),
+            ScheduleMessage: CreateMessageRef(input));
+
+    private static PlatformUser CreateUser(DiscordSessionInteractionInput input) =>
+        new(
+            PlatformKind.Discord,
+            input.UserId.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            string.IsNullOrWhiteSpace(input.DisplayName) ? input.Username : input.DisplayName,
+            input.Username);
+
+    private static PlatformGroup CreateGroup(DiscordSessionInteractionInput input) =>
+        new(
+            PlatformKind.Discord,
+            input.GuildId,
+            input.GuildId,
+            input.ChannelId);
+
+    private static PlatformMessageRef CreateMessageRef(DiscordSessionInteractionInput input) =>
+        new(
+            PlatformKind.Discord,
+            input.GuildId,
+            null,
+            input.MessageId);
+}

src/GmRelay.DiscordBot/Features/Sessions/DiscordSessionInteractionModule.cs

@@ -0,0 +1,101 @@
+using GmRelay.DiscordBot.Infrastructure.Discord;
+using GmRelay.Shared.Features.Sessions.CreateSession;
+using NetCord;
+using NetCord.Rest;
+using NetCord.Services.ComponentInteractions;
+
+namespace GmRelay.DiscordBot.Features.Sessions;
+
+public sealed class DiscordSessionInteractionModule(
+    JoinSessionHandler joinSessionHandler,
+    LeaveSessionHandler leaveSessionHandler,
+    DiscordInteractionReplyCache interactionReplies,
+    ILogger<DiscordSessionInteractionModule> logger) : ComponentInteractionModule<ButtonInteractionContext>
+{
+    [ComponentInteraction("join_session")]
+    public async Task JoinAsync(string sessionId)
+    {
+        if (!Guid.TryParse(sessionId, out var parsedSessionId))
+        {
+            await RespondAsync(CreateEphemeralReply("Session button is outdated."));
+            return;
+        }
+
+        var input = CreateInput(parsedSessionId);
+        await RespondAsync(InteractionCallback.DeferredMessage(MessageFlags.Ephemeral));
+        try
+        {
+            await joinSessionHandler.HandleAsync(
+                DiscordSessionInteractionMapper.CreateJoinCommand(input),
+                CancellationToken.None);
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to handle Discord join interaction for session {SessionId}", parsedSessionId);
+            await CompleteResponseAsync("Не удалось обработать кнопку.");
+            return;
+        }
+
+        await CompleteWithStoredReplyAsync(input.InteractionId);
+    }
+
+    [ComponentInteraction("leave_session")]
+    public async Task LeaveAsync(string sessionId)
+    {
+        if (!Guid.TryParse(sessionId, out var parsedSessionId))
+        {
+            await RespondAsync(CreateEphemeralReply("Session button is outdated."));
+            return;
+        }
+
+        var input = CreateInput(parsedSessionId);
+        await RespondAsync(InteractionCallback.DeferredMessage(MessageFlags.Ephemeral));
+        try
+        {
+            await leaveSessionHandler.HandleAsync(
+                DiscordSessionInteractionMapper.CreateLeaveCommand(input),
+                CancellationToken.None);
+        }
+        catch (Exception ex)
+        {
+            logger.LogError(ex, "Failed to handle Discord leave interaction for session {SessionId}", parsedSessionId);
+            await CompleteResponseAsync("Не удалось обработать кнопку.");
+            return;
+        }
+
+        await CompleteWithStoredReplyAsync(input.InteractionId);
+    }
+
+    private DiscordSessionInteractionInput CreateInput(Guid sessionId)
+    {
+        var guild = Context.Guild
+            ?? throw new InvalidOperationException("Session buttons can only be used in a guild.");
+        var message = Context.Interaction.Message
+            ?? throw new InvalidOperationException("Session button interaction must include a message.");
+
+        return new DiscordSessionInteractionInput(
+            SessionId: sessionId,
+            InteractionId: Context.Interaction.Id.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            GuildId: guild.Id.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            ChannelId: Context.Channel.Id.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            MessageId: message.Id.ToString(System.Globalization.CultureInfo.InvariantCulture),
+            UserId: Context.User.Id,
+            Username: Context.User.Username,
+            DisplayName: Context.User.GlobalName);
+    }
+
+    private async Task CompleteWithStoredReplyAsync(string interactionId)
+    {
+        var reply = interactionReplies.Take(interactionId);
+        await CompleteResponseAsync(reply?.Text ?? "Session updated.");
+    }
+
+    private Task CompleteResponseAsync(string text) =>
+        ModifyResponseAsync(options => options.Content = text);
+
+    private static InteractionCallbackProperties CreateEphemeralReply(string text) =>
+        InteractionCallback.Message(
+            new InteractionMessageProperties()
+                .WithContent(text)
+                .WithFlags(MessageFlags.Ephemeral));
+}