Remove unused directive and update Transformer summary

Removed the `using System.Diagnostics;` directive. Retained the namespace declaration for `Open.Database.Extensions`. Added a summary comment to the `Transformer<T>` class constructor to clarify its purpose and the optional field mapping overrides parameter.

Author: electricessence

Source/Channel/Transformer.cs

@@ -1,6 +1,4 @@
-using System.Diagnostics;
-
-namespace Open.Database.Extensions;
+namespace Open.Database.Extensions;
 
 /// <summary>Constructs a <see cref="Transformer{T}"/>.</summary>
 /// <param name="fieldMappingOverrides">An optional override map of field names to column names where the keys are the property names, and values are the column names.</param>