Add bumper variant management: implement API endpoints for adding, updating, and removing bumper text variants, enhance data models to support variant details, and update scheduling logic to utilize variants. Refactor related components for improved bumper template handling and ensure proper error management for variant operations.

backend/src/TeleWave.Application/Broadcast/Bumpers/AddBumperTextVariantCommandHandler.cs

@@ -0,0 +1,33 @@
+using LiteCqrs;
+using Microsoft.EntityFrameworkCore;
+using TeleWave.Application.Common.Interfaces;
+using TeleWave.Application.Common.Models;
+
+namespace TeleWave.Application.Broadcast.Bumpers;
+
+public sealed class AddBumperTextVariantCommandHandler(IAppDbContext dbContext)
+    : ICommandHandler<AddBumperTextVariantCommand, Result<Guid>>
+{
+    public async Task<Result<Guid>> Handle(
+        AddBumperTextVariantCommand command,
+        CancellationToken cancellationToken
+    )
+    {
+        var channel = await dbContext.Channels
+            .Include(c => c.BumperTemplates)
+            .ThenInclude(t => t.Variants)
+            .FirstOrDefaultAsync(c => c.Id == command.ChannelId, cancellationToken);
+        if (channel is null)
+            return Result.Failure<Guid>(ChannelErrors.NotFound);
+
+        var template = channel.FindBumperTemplate(command.TemplateId);
+        if (template is null)
+            return Result.Failure<Guid>(ChannelErrors.BumperTemplateNotFound);
+
+        var name = string.IsNullOrWhiteSpace(command.Name)
+            ? $"Текст {template.Variants.Count + 1}"
+            : command.Name.Trim();
+        var variant = template.AddVariant(name);
+        return Result.Success(variant.Id);
+    }
+}