fix editing channel number (#59)

ErsatzTV.Application/Channels/Commands/CreateChannelHandler.cs

@@ -74,7 +74,7 @@ namespace ErsatzTV.Application.Channels.Commands
                 _ => BaseError.New("Channel number must be unique"),
                 () =>
                 {
-                    if (Regex.IsMatch(createChannel.Number, @"^[0-9]+(\.[0-9])?$"))
+                    if (Regex.IsMatch(createChannel.Number, Channel.NumberValidator))
                     {
                         return createChannel.Number;
                     }

ErsatzTV.Application/Channels/Commands/UpdateChannelHandler.cs

@@ -82,7 +82,7 @@ namespace ErsatzTV.Application.Channels.Commands
             int matchId = match.Map(c => c.Id).IfNone(updateChannel.ChannelId);
             if (matchId == updateChannel.ChannelId)
             {
-                if (Regex.IsMatch(updateChannel.Number, @"^[0-9](\.[0-9])?$"))
+                if (Regex.IsMatch(updateChannel.Number, Channel.NumberValidator))
                 {
                     return updateChannel.Number;
                 }

ErsatzTV.Core/Domain/Channel.cs

@@ -5,6 +5,8 @@ namespace ErsatzTV.Core.Domain
 {
     public class Channel
     {
+        public static string NumberValidator = @"^[0-9]+(\.[0-9])?$";
+
         public Channel(Guid uniqueId) => UniqueId = uniqueId;
         public int Id { get; set; }
         public Guid UniqueId { get; init; }

ErsatzTV/Validators/ChannelEditViewModelValidator.cs

@@ -1,4 +1,5 @@
-using ErsatzTV.ViewModels;
+using ErsatzTV.Core.Domain;
+using ErsatzTV.ViewModels;
 using FluentValidation;
 
 namespace ErsatzTV.Validators
@@ -7,7 +8,7 @@ namespace ErsatzTV.Validators
     {
         public ChannelEditViewModelValidator()
         {
-            RuleFor(x => x.Number).Matches(@"^[0-9]+(\.[0-9])?$")
+            RuleFor(x => x.Number).Matches(Channel.NumberValidator)
                 .WithMessage("Invalid channel number; one decimal is allowed for subchannels");
 
             RuleFor(x => x.Name).NotEmpty();