add IInsinTelemetry and NullInsinTelemetry

Inspectron.Epson.Tests/Telemetry/NullInsinTelemetryTests.cs

@@ -0,0 +1,14 @@
+using Inspectron.Epson.PrintServer.Telemetry;
+
+namespace Inspectron.Epson.Tests.Telemetry;
+
+public class NullInsinTelemetryTests
+{
+    [Fact]
+    public void Emit_does_nothing_and_does_not_throw()
+    {
+        var telemetry = new NullInsinTelemetry();
+        var ex = Record.Exception(() => telemetry.Emit("service.started", "version=1.0.0"));
+        Assert.Null(ex);
+    }
+}

Inspectron.Epson/PrintServer/Telemetry/IInsinTelemetry.cs

@@ -0,0 +1,6 @@
+namespace Inspectron.Epson.PrintServer.Telemetry;
+
+public interface IInsinTelemetry
+{
+    void Emit(string kind, string message);
+}

Inspectron.Epson/PrintServer/Telemetry/NullInsinTelemetry.cs

@@ -0,0 +1,6 @@
+namespace Inspectron.Epson.PrintServer.Telemetry;
+
+public sealed class NullInsinTelemetry : IInsinTelemetry
+{
+    public void Emit(string kind, string message) { }
+}