Add instance id support

ErsatzTV.Core/Iptv/ChannelIdentifier.cs

@@ -17,6 +17,6 @@ public static class ChannelIdentifier
             number /= 10;
         }
 
-        return $"C{channelNumber}.{id}.ersatztv.org";
+        return $"C{channelNumber}.{id}.{SystemEnvironment.InstanceID}";
     }
 }

ErsatzTV.Core/SystemEnvironment.cs

@@ -10,6 +10,8 @@ public class SystemEnvironment
 
         TranscodeFolder = Environment.GetEnvironmentVariable("ETV_TRANSCODE_FOLDER");
 
+        InstanceID = Environment.GetEnvironmentVariable("ETV_INSTANCE_ID");
+
         string uiPortVariable = Environment.GetEnvironmentVariable("ETV_UI_PORT");
         if (!int.TryParse(uiPortVariable, out int uiPort))
         {
@@ -71,4 +73,5 @@ public class SystemEnvironment
     public static int? SlowApiMs { get; }
     public static int JellyfinPageSize { get; }
     public static bool JellyfinEnableStats { get; }
+    public static string InstanceID { get; }
 }

ErsatzTV/Properties/launchSettings.json

@@ -7,7 +7,8 @@
         "ASPNETCORE_ENVIRONMENT": "Development",
         "DOTNET_ENVIRONMENT": "Development",
         "ETV_STREAMING_PORT": "8409",
-        "ETV_UI_PORT": "8410"
+        "ETV_UI_PORT": "8410",
+        "ETV_INSTANCE_ID": "ersatztv.org"
       }
     }
   }