Add EnvelopeGenerator.Service as a .NET Worker Service

Introduced a new project `EnvelopeGenerator.Service` to the solution as a .NET Worker Service targeting the `net4.6.2` framework.

- Configured the project with nullable reference types, implicit usings, and `LangVersion` set to `latest`.
- Added a `Worker` class that logs periodic messages while running.
- Updated `Program.cs` to configure and run the Worker Service.
- Added `launchSettings.json` for development environment configuration.
- Added `appsettings.json` and `appsettings.Development.json` for logging configuration.
- Included the project in `EnvelopeGenerator.sln` with appropriate build configurations and hierarchy updates.

EnvelopeGenerator.Service/EnvelopeGenerator.Service.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk.Worker">
+
+  <PropertyGroup>
+    <TargetFrameworks>net4.6.2</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <UserSecretsId>dotnet-EnvelopeGenerator.Service-816256a4-c636-4313-92c0-b62b04040c2b</UserSecretsId>
+	<LangVersion>latest</LangVersion>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.Hosting" Version="8.0.1" />
+  </ItemGroup>
+</Project>

EnvelopeGenerator.Service/Program.cs

@@ -0,0 +1,7 @@
+using EnvelopeGenerator.Service;
+
+var builder = Host.CreateApplicationBuilder(args);
+builder.Services.AddHostedService<Worker>();
+
+var host = builder.Build();
+host.Run();

EnvelopeGenerator.Service/Properties/launchSettings.json

@@ -0,0 +1,12 @@
+{
+  "$schema": "http://json.schemastore.org/launchsettings.json",
+  "profiles": {
+    "EnvelopeGenerator.Service": {
+      "commandName": "Project",
+      "dotnetRunMessages": true,
+      "environmentVariables": {
+        "DOTNET_ENVIRONMENT": "Development"
+      }
+    }
+  }
+}

EnvelopeGenerator.Service/Worker.cs

@@ -0,0 +1,24 @@
+namespace EnvelopeGenerator.Service
+{
+    public class Worker : BackgroundService
+    {
+        private readonly ILogger<Worker> _logger;
+
+        public Worker(ILogger<Worker> logger)
+        {
+            _logger = logger;
+        }
+
+        protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+        {
+            while (!stoppingToken.IsCancellationRequested)
+            {
+                if (_logger.IsEnabled(LogLevel.Information))
+                {
+                    _logger.LogInformation("Worker running at: {time}", DateTimeOffset.Now);
+                }
+                await Task.Delay(1000, stoppingToken);
+            }
+        }
+    }
+}

EnvelopeGenerator.Service/appsettings.Development.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.Hosting.Lifetime": "Information"
+    }
+  }
+}

EnvelopeGenerator.Service/appsettings.json

@@ -0,0 +1,8 @@
+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.Hosting.Lifetime": "Information"
+    }
+  }
+}