Introduced new GetVersion() extension

When we introduced the `GetDateTime()` extension method in #dde0ade, we inadvertantly reduced the precision of the `DateTime` value returned. This is a problem since this is used for `Version` (e.g., when setting the `VersionHistory`) and that's a place where the precision must match the database exactly. Unfortunately, the logic for this is a bit different than it is for other types, since it's the interstitial string conversion that's introducing the problem here. To mitigate that, we must duplicate some of the logic from the private `GetValue<T>()` in order to explicitly avoid that conversion, and instead pull the value explicitly using the `GetDateTime()` method. This process won't actually work with other types of `DateTime` values, such as those encoded as a string in the `Attributes` table. As such, to differentiate these, this is being introduced as `GetVersion()`.

Author: JeremyCaney

OnTopic.Data.Sql/SqlDataReaderExtensions.cs

@@ -58,6 +58,16 @@ internal static string GetString(this SqlDataReader reader, string columnName) =
     internal static DateTime GetDateTime(this SqlDataReader reader, string columnName) =>
       GetValue<DateTime>(reader, columnName, DateTime.TryParse, DateTime.MinValue);
 
+    /*==========================================================================================================================
+    | METHOD: GET VERSION
+    \-------------------------------------------------------------------------------------------------------------------------*/
+    /// <summary>
+    ///   Retrieves the version column, with precisions appropriate for setting the <see cref="Topic.VersionHistory"/>.
+    /// </summary>
+    /// <param name="reader">The <see cref="SqlDataReader"/> object.</param>
+    internal static DateTime GetVersion(this SqlDataReader reader) =>
+      reader.GetDateTime(reader.GetOrdinal("Version"));
+
     /*==========================================================================================================================
     | METHOD: GET BOOLEAN
     \-------------------------------------------------------------------------------------------------------------------------*/

OnTopic.Data.Sql/SqlTopicRepository.cs

@@ -118,7 +118,7 @@ private static void SetIndexedAttributes(SqlDataReader reader, Dictionary<int, T
       //Check field count to avoid breaking changes with the 4.0.0 release, which didn't include a "Version" column
       //### TODO JJC20200221: This condition can be removed and accepted as a breaking change in v5.0.
       if (reader.FieldCount > 3) {
-        version                 = reader.GetDateTime("Version");
+        version                 = reader.GetVersion();
       }
 
       /*------------------------------------------------------------------------------------------------------------------------
@@ -173,7 +173,7 @@ private static void SetExtendedAttributes(SqlDataReader reader, Dictionary<int,
       //Check field count to avoid breaking changes with the 4.0.0 release, which didn't include a "Version" column
       //### TODO JJC20200221: This condition can be removed and accepted as a breaking change in v5.0.
       if (reader.FieldCount > 2) {
-        version                 = reader.GetDateTime("Version");
+        version                 = reader.GetVersion();
       }
 
       /*------------------------------------------------------------------------------------------------------------------------
@@ -331,7 +331,7 @@ private static void SetVersionHistory(SqlDataReader reader, Dictionary<int, Topi
       | Identify attributes
       \-----------------------------------------------------------------------------------------------------------------------*/
       var sourceTopicId         = reader.GetInteger("TopicID");
-      var dateTime              = reader.GetDateTime("Version");
+      var dateTime              = reader.GetVersion();
 
       /*------------------------------------------------------------------------------------------------------------------------
       | Identify topic