Inject Referrer URL to Azure App Insights for Sitecore Instance

AddReferrerToTelemetry.cs

using Microsoft.ApplicationInsights.Channel;
using Microsoft.ApplicationInsights.DataContracts;
using Microsoft.ApplicationInsights.Extensibility;
using Sitecore.Pipelines.HttpRequest;
using System.Web;

namespace Sitecore.Foundation.SitecoreExtensions.Pipelines.HttpRequestBegin
{
  public class AddReferrerToTelemetry : HttpRequestProcessor
  {
    public override void Process(HttpRequestArgs args) => AddReferrerToTelemetry.Inject();

    public static void Inject()
    {
      TelemetryConfiguration.Active.TelemetryInitializers.Add((ITelemetryInitializer)new ReferrerInitializer());
    }
  }

  public class ReferrerInitializer : ITelemetryInitializer
  {
    public void Initialize(ITelemetry telemetry)
    {
      if (telemetry is RequestTelemetry requestTelemetry)
      {
        var httpContext = HttpContext.Current;
        if (httpContext?.Request == null)
        {
          return;
        }
        var request = httpContext.Request;
        requestTelemetry.Properties["Referrer"] = request.UrlReferrer.AbsoluteUri;
      }
    }
  }
}

Sitecore.AddReferrerToTelemetry.config

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" 
               xmlns:role="http://www.sitecore.net/xmlconfig/role/" 
               xmlns:useApplicationInsights="http://www.sitecore.net/xmlconfig/useApplicationInsights/">
  <sitecore>
      <httpRequestBegin>
        <processor type="Sitecore.Foundation.SitecoreExtensions.Pipelines.HttpRequestBegin.AddReferrerToTelemetry, 
                   Sitecore.Foundation.SitecoreExtensions"
                   resolve="true"
                   patch:before="*[1]" 
                   useApplicationInsights:require="!false" />
  </sitecore>
</configuration>