Make PublishedContentQueryAccessor usable (#11601)

* Make PublishedContentQueryAccessor usable

Closes #11319

* Make xmldocs for IPublishedContentQueryAccessor more helpful.

tests/Umbraco.Tests.Integration/Umbraco.Core/PublishedContentQueryAccessorTests.cs

@@ -0,0 +1,45 @@
+using System;
+using System.Net;
+using System.Net.Http;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Mvc;
+using NUnit.Framework;
+using Umbraco.Cms.Core;
+using Umbraco.Cms.Tests.Integration.TestServerTest;
+
+namespace Umbraco.Cms.Tests.Integration.Umbraco.Core
+{
+    [TestFixture]
+    public class PublishedContentQueryAccessorTests : UmbracoTestServerTestBase
+    {
+        [Test]
+        public async Task PublishedContentQueryAccessor_WithRequestScope_WillProvideQuery()
+        {
+            HttpResponseMessage result = await Client.GetAsync("/demo-published-content-query-accessor");
+            Assert.AreEqual(HttpStatusCode.OK, result.StatusCode);
+        }
+    }
+
+    public class PublishedContentQueryAccessorTestController : Controller
+    {
+        private readonly IPublishedContentQueryAccessor _accessor;
+
+        public PublishedContentQueryAccessorTestController(IPublishedContentQueryAccessor accessor)
+        {
+            _accessor = accessor;
+        }
+
+        [HttpGet("demo-published-content-query-accessor")]
+        public IActionResult Test()
+        {
+            var success = _accessor.TryGetValue(out IPublishedContentQuery query);
+
+            if (!success || query == null)
+            {
+                throw new ApplicationException("It doesn't work");
+            }
+
+            return Ok();
+        }
+    }
+}