fix: #143 Add comments to explain algo

Author: driccio

src/TransformOperationExecutor.ts

@@ -167,10 +167,13 @@ export class TransformOperationExecutor {
                     let finalValue;
 
                     if (this.transformationType === TransformationType.CLASS_TO_PLAIN) {
+                        // Get original value
                         finalValue = value[transformKey];
+                        // Apply custom transformation
                         finalValue = this.applyCustomTransformations(finalValue, targetType, transformKey, value, this.transformationType);
+                        // If nothing change, it means no custom transformation was applied, so use the subValue.
                         finalValue = (value[transformKey] === finalValue) ? subValue : finalValue;
-                        // value[transformKey] = finalValue;
+                        // Apply the default transformation
                         finalValue = this.transform(subSource, finalValue, type, arrayType, isSubValueMap, level + 1);
                     } else {
                         finalValue = this.transform(subSource, subValue, type, arrayType, isSubValueMap, level + 1);