docs: add info on how to use serilog env vars to enable logging (#249)

Author: petar-i-todorov

dotnet-docs/logging.md

@@ -14,10 +14,31 @@ The Report Server for .NET uses [Serilog](https://serilog.net/) to allow  writin
 
 ## Setup
 
-The configuration options for Serilog that would usually be set up through the C# API - [Serilog Configuration Basics](https://github.com/serilog/serilog/wiki/Configuration-Basics), can instead be
-defined in the `appsettings.json` configuration files of the Report Server for .NET.
+The configuration options for Serilog that would usually be set up through the C# API - [Serilog Configuration Basics](https://github.com/serilog/serilog/wiki/Configuration-Basics), can be configured in two ways:
 
-### Report Server Manager
+1. [Environment Variables](#using-environment-variables) - Set system-wide environment variables.
+2. [Configuration Files](#using-configuration-files) - Modify the `appsettings.json` files directly.
+
+### Using Environment Variables
+
+You can enable logging for both the Report Server Manager and Service Agent at the same time by setting the following environment variables:
+
+````
+Serilog__MinimumLevel=Verbose
+Serilog__WriteTo__1__Name=File
+Serilog__WriteTo__1__Args__path=Logs/rsnetlogs.txt
+````
+
+This requires the default Serilog configuration to exist in the `appsettings.json` files for both the manager and service components, as environment variables are intended to override these base settings as needed.
+
+>note When the Report Server is installed using the MSI installer, it runs under a dedicated Windows user account (ReportServerUser) or a system account (e.g., LocalSystem) depending on your installation choice. These accounts do not have access to user-level environment variables. 
+> To ensure environment variable overrides work correctly, you must define them at the **system level**.
+
+### Using Configuration Files
+
+Alternatively, you can define the configuration in the `appsettings.json` configuration files of the Report Server for .NET.
+
+#### Report Server Manager
 
 The `appsettings.json` file of the Report Server Manager for .NET resides in its installation directory, for example, `C:\Program Files (x86)\Progress\Telerik Report Server\Telerik.ReportServer.Web.NET\`.
 The following configuration settings can be added to that file, at the top level:
@@ -37,7 +58,7 @@ The following configuration settings can be added to that file, at the top level
   }
 ````
 
-### Service Agent
+#### Service Agent
 
 The Report Server for .NET ServiceAgent's `appsettings.json` file can be found in its installation directory, by default - `C:\Program Files (x86)\Progress\Telerik Report Server\Services\.NET\`.
 The following configuration settings can be added to that file, at the top level: