Add ASP.NET Core logging example

docs/logs/getting-started-aspnetcore/Program.cs

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+// <copyright file="Program.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using OpenTelemetry.Logs;
+using OpenTelemetry.Resources;
+
+var builder = WebApplication.CreateBuilder(args);
+
+builder.Logging.AddOpenTelemetry(logging =>
+{
+    logging.IncludeScopes = true;
+    logging.ParseStateValues = true;
+
+    var resourceBuilder = ResourceBuilder
+        .CreateDefault()
+        .AddService(builder.Environment.ApplicationName);
+
+    logging.SetResourceBuilder(resourceBuilder)
+        .AddConsoleExporter();
+});
+
+var app = builder.Build();
+
+app.MapGet("/", (ILogger<Program> logger) =>
+{
+    logger.FoodPriceChanged("artichoke", 9.99);
+
+    return "Hello from OpenTelemetry Logs!";
+});
+
+app.Logger.StartingApp();
+
+app.Run();
+
+public static partial class ApplicationLogs
+{
+    [LoggerMessage(EventId = 1, Level = LogLevel.Information, Message = "Starting the app...")]
+    public static partial void StartingApp(this ILogger logger);
+
+    [LoggerMessage(EventId = 2, Level = LogLevel.Information, Message = "Food `{name}` price changed to `{price}`.")]
+    public static partial void FoodPriceChanged(this ILogger logger, string name, double price);
+}

docs/logs/getting-started-aspnetcore/README.md

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+# Getting Started with OpenTelemetry .NET Logs in 5 Minutes - ASP.NET Core Application
+
+First, download and install the [.NET
+SDK](https://dotnet.microsoft.com/download) on your computer.
+
+Create a new web application:
+
+```sh
+dotnet new web -o aspnetcoreapp
+cd aspnetcoreapp
+```
+
+Install the
+[OpenTelemetry.Exporter.Console](../../../src/OpenTelemetry.Exporter.Console/README.md)
+and
+[OpenTelemetry.Extensions.Hosting](../../../src/OpenTelemetry.Extensions.Hosting/README.md)
+packages:
+
+```sh
+dotnet add package OpenTelemetry.Exporter.Console
+dotnet add package OpenTelemetry.Extensions.Hosting
+```
+
+Update the `Program.cs` file with the code from [Program.cs](./Program.cs).
+
+Run the application again (using `dotnet run`) and then browse to the URL shown
+in the console for your application (e.g. `http://localhost:5000`). You should see
+the logs output from the console.
+
+```text
+LogRecord.Timestamp:               2023-09-06T22:59:17.9787564Z
+LogRecord.CategoryName:            getting-started-aspnetcore
+LogRecord.Severity:                Info
+LogRecord.SeverityText:            Information
+LogRecord.Body:                    Starting the app...
+LogRecord.Attributes (Key:Value):
+    OriginalFormat (a.k.a Body): Starting the app...
+LogRecord.EventId:                 1
+LogRecord.EventName:               StartingApp
+
+Resource associated with LogRecord:
+service.name: getting-started-aspnetcore
+service.instance.id: d62727d2-3e80-4780-a984-e85fc861e321
+telemetry.sdk.name: opentelemetry
+telemetry.sdk.language: dotnet
+telemetry.sdk.version: 1.6.0-rc.1.24
+
+LogRecord.Timestamp:               2023-09-06T22:59:18.0644378Z
+LogRecord.CategoryName:            Microsoft.Hosting.Lifetime
+LogRecord.Severity:                Info
+LogRecord.SeverityText:            Information
+LogRecord.Body:                    Now listening on: {address}
+LogRecord.Attributes (Key:Value):
+    address: http://localhost:5000
+    OriginalFormat (a.k.a Body): Now listening on: {address}
+LogRecord.EventId:                 14
+LogRecord.EventName:               ListeningOnAddress
+
+Resource associated with LogRecord:
+service.name: getting-started-aspnetcore
+service.instance.id: d62727d2-3e80-4780-a984-e85fc861e321
+telemetry.sdk.name: opentelemetry
+telemetry.sdk.language: dotnet
+telemetry.sdk.version: 1.6.0-rc.1.24
+
+LogRecord.Timestamp:               2023-09-06T23:00:46.1639248Z
+LogRecord.TraceId:                 3507087d60ae4b1d2f10e68f4e40784a
+LogRecord.SpanId:                  c51be9f19c598b69
+LogRecord.TraceFlags:              None
+LogRecord.CategoryName:            Program
+LogRecord.Severity:                Info
+LogRecord.SeverityText:            Information
+LogRecord.Body:                    Food `{name}` price changed to `{price}`.
+LogRecord.Attributes (Key:Value):
+    name: artichoke
+    price: 9.99
+    OriginalFormat (a.k.a Body): Food `{name}` price changed to `{price}`.
+LogRecord.EventId:                 2
+LogRecord.EventName:               FoodPriceChanged
+LogRecord.ScopeValues (Key:Value):
+[Scope.0]:SpanId: c51be9f19c598b69
+[Scope.0]:TraceId: 3507087d60ae4b1d2f10e68f4e40784a
+[Scope.0]:ParentId: 0000000000000000
+[Scope.1]:ConnectionId: 0HMTF5KCP0BU9
+[Scope.2]:RequestId: 0HMTF5KCP0BU9:00000003
+[Scope.2]:RequestPath: /
+
+Resource associated with LogRecord:
+service.name: getting-started-aspnetcore
+service.instance.id: d62727d2-3e80-4780-a984-e85fc861e321
+telemetry.sdk.name: opentelemetry
+telemetry.sdk.language: dotnet
+telemetry.sdk.version: 1.6.0-rc.1.24
+```
+
+Congratulations! You are now collecting logs using OpenTelemetry.
+
+What does the above program do?
+
+The program has added OpenTelemetry as a [logging
+provider](https://learn.microsoft.com/dotnet/core/extensions/logging-providers)
+to the existing logging pipeline. OpenTelemetry SDK is then configured with a
+`ConsoleExporter` to export the logs to the console. In addition,
+`OpenTelemetryLoggerOptions.IncludeScopes` is enabled so the logs will include
+the [log
+scopes](https://learn.microsoft.com/dotnet/core/extensions/logging#log-scopes).
+From the console output we can see the log scopes that are coming from the
+ASP.NET Core framework, and we can see logs from both our logger and the ASP.NET
+Core framework loggers.
+
+The example has demonstrated the best practice from ASP.NET Core by injecting
+generic `ILogger<T>`:
+
+```csharp
+app.MapGet("/", (ILogger<Program> logger) =>
+{
+    logger.FoodPriceChanged("artichoke", 9.99);
+
+    return "Hello from OpenTelemetry Logs!";
+});
+```
+
+To achieve structured logging and high performance, [Compile-time logging source
+generation](https://docs.microsoft.com/dotnet/core/extensions/logger-message-generator)
+is used:
+
+```csharp
+public static partial class ApplicationLogs
+{
+    [LoggerMessage(EventId = 1, Level = LogLevel.Information, Message = "Starting the app...")]
+    public static partial void StartingApp(this ILogger logger);
+
+    [LoggerMessage(EventId = 2, Level = LogLevel.Information, Message = "Food `{name}` price changed to `{price}`.")]
+    public static partial void FoodPriceChanged(this ILogger logger, string name, double price);
+}
+```
+
+For logs that occur between `builder.Build()` and `app.Run()` when
+injecting a generic `ILogger<T>` is not an option, `app.Logger` is used instead:
+
+```csharp
+app.Logger.StartingApp();
+```
+
+## Learn more
+
+* [Compile-time logging source
+  generation](https://docs.microsoft.com/dotnet/core/extensions/logger-message-generator)
+* [Customizing the OpenTelemetry .NET SDK](../customizing-the-sdk/README.md)
+* [Extending the OpenTelemetry .NET SDK](../extending-the-sdk/README.md)

docs/logs/getting-started-aspnetcore/appsettings.Development.json

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+{
+  "DetailedErrors": true,
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  }
+}

docs/logs/getting-started-aspnetcore/appsettings.json

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+{
+  "Logging": {
+    "LogLevel": {
+      "Default": "Information",
+      "Microsoft.AspNetCore": "Warning"
+    }
+  },
+  "AllowedHosts": "*"
+}

docs/logs/getting-started-aspnetcore/getting-started-aspnetcore.csproj

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+<Project Sdk="Microsoft.NET.Sdk.Web">
+
+  <PropertyGroup>
+    <TargetFrameworks>net6.0;net7.0</TargetFrameworks>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.Exporter.Console\OpenTelemetry.Exporter.Console.csproj" />
+    <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.Extensions.Hosting\OpenTelemetry.Extensions.Hosting.csproj" />
+  </ItemGroup>
+
+</Project>