Add logging documentation for layered web application solution template

docs/en/solution-templates/layered-web-application/logging.md

@@ -0,0 +1,35 @@
+# Layered Solution: Logging
+
+```json
+//[doc-nav]
+{
+  "Previous": {
+    "Name": "Database configurations",
+    "Path": "solution-templates/layered-web-application/database-configurations"
+  },
+  "Next": {
+    "Name": "Swagger integration",
+    "Path": "solution-templates/layered-web-application/swagger-integration"
+  }
+}
+```
+
+The ABP Studio [layered solution template](index.md) is fully configured for [logging](../../framework/fundamentals/logging.md). All the applications are configured to use the [Serilog](https://serilog.net/) library for structured logging. They are configured in a common way for logging. This document explains that common logging structure.
+
+## The Serilog Sinks
+
+The Serilog library is configured so it writes the logs to the following targets (a.k.a. [sinks](https://github.com/serilog/serilog/wiki/Provided-Sinks)) in parallel:
+
+* **[Console](https://github.com/serilog/serilog-sinks-console)**: Logs are written to the standard output of the executing application. Logging to console is useful when you want to see logs easily while it is running in a container.
+* **[File](https://github.com/serilog/serilog-sinks-file)**: Logs are written to a file named `logs.txt` located under the `Logs` folder of the executing application. File logging is useful when you run the application on your local computer. You can check logs easily when you have a trouble. This sinks is only configured for DEBUG mode. It won't be available in your production environment (you can change the behavior in your `Program.cs` file).
+* **ABP Studio**: This is a Sink provided by ABP Studio. It sends all logs to ABP Studio, so you can easily monitor your logs in real-time on your ABP Studio Application Monitoring panel.
+
+The solution can work with [any sink](https://github.com/serilog/serilog/wiki/Provided-Sinks) supported by Serilog. You can add more sinks, remove pre-installed sinks or fine tune their configuration for your solution.
+
+## Program.cs
+
+The `Program.cs` file is the main point that configures the logging system. It is done here, because we want to initialize and start the logging in the very beginning of the application.
+
+## Additional Information
+
+We are using ABP Serilog Enrichers in the module class of the application. It is done by the `app.UseAbpSerilogEnrichers();` line in the `OnApplicationInitialization` method of your module class. That ASP.NET Core middleware adds current [tenant](../../framework/architecture/multi-tenancy/index.md), [user](../../framework/infrastructure/current-user.md), client and correlation id information to the log records.