chore: add TODO items for the next refactoring steps.

Addressed to #927

[skip ci]

Author: php-coder

src/main/java/ru/mystamps/web/feature/category/CategoryController.java

@@ -84,6 +84,8 @@ public String processInput(
 		return redirectTo(CategoryUrl.INFO_CATEGORY_PAGE, slug);
 	}
 
+	// CheckStyle: ignore LineLength for next 1 line
+	// @todo #927 CategoryController: remove dependency on SeriesService by moving showInfoBySlug() method
 	@GetMapping(CategoryUrl.INFO_CATEGORY_PAGE)
 	public String showInfoBySlug(
 		@Category @PathVariable("slug") LinkEntityDto category,

src/main/java/ru/mystamps/web/feature/country/CountryController.java

@@ -84,6 +84,8 @@ public String processInput(
 		return redirectTo(CountryUrl.INFO_COUNTRY_PAGE, slug);
 	}
 
+	// CheckStyle: ignore LineLength for next 1 line
+	// @todo #927 CountryController: remove dependency on SeriesService by moving showInfoBySlug() method
 	@GetMapping(CountryUrl.INFO_COUNTRY_PAGE)
 	public String showInfoBySlug(
 		@Country @PathVariable("slug") LinkEntityDto country,

src/main/java/ru/mystamps/web/feature/series/PurchaseAndSaleDto.java

@@ -24,6 +24,7 @@
 import java.math.BigDecimal;
 import java.util.Date;
 
+// @todo #927 PurchaseAndSaleDto: move with related classes to series.sale package
 /**
  * @author Sergey Chechenev
  */