Update scheduling parameters and refactor channel endpoints: extend HorizonDays to 7 and RetentionDays to 90 in appsettings.json. Consolidate channel-related endpoint logic by removing obsolete files and enhancing the ShowEndpoints with audience and genre management capabilities. Improve error handling and streamline command handlers for channel operations.

backend/src/TeleWave.Application/Programming/Groups/CreateGroup/CreateGroupCommandValidator.cs

@@ -0,0 +1,12 @@
+using FluentValidation;
+
+namespace TeleWave.Application.Programming.Groups.CreateGroup;
+
+public sealed class CreateGroupCommandValidator : AbstractValidator<CreateGroupCommand>
+{
+    public CreateGroupCommandValidator()
+    {
+        RuleFor(x => x.Name).NotEmpty().MaximumLength(256);
+        RuleFor(x => x.Description).MaximumLength(2048);
+    }
+}