Refine XML docs for historian, OPC UA, and tests

tests/ZB.MOM.WW.LmxOpcUa.Tests/Integration/HistorizingFlagTests.cs

@@ -27,6 +27,9 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Integration
             };
         }
 
+        /// <summary>
+        /// Verifies that historized Galaxy attributes advertise OPC UA historizing support and history-read access.
+        /// </summary>
         [Fact]
         public async Task HistorizedAttribute_HasHistorizingTrue_AndHistoryReadAccess()
         {
@@ -49,6 +52,9 @@ namespace ZB.MOM.WW.LmxOpcUa.Tests.Integration
             finally { await fixture.DisposeAsync(); }
         }
 
+        /// <summary>
+        /// Verifies that non-historized Galaxy attributes do not claim OPC UA history support.
+        /// </summary>
         [Fact]
         public async Task NormalAttribute_HasHistorizingFalse_AndNoHistoryReadAccess()
         {