improve: detect US dollar currency when the price is prefixed with "US$"

Author: php-coder

src/main/java/ru/mystamps/web/feature/series/importing/SeriesInfoExtractorServiceImpl.java

@@ -85,7 +85,7 @@ public class SeriesInfoExtractorServiceImpl implements SeriesInfoExtractorServic
 	private static final Pattern UAH_CURRENCY_REGEXP = Pattern.compile("([0-9] |\\b)грн\\b");
 
 	// Regular expression that matches US dollar.
-	private static final Pattern USD_CURRENCY_REGEXP = Pattern.compile("[0-9]\\$");
+	private static final Pattern USD_CURRENCY_REGEXP = Pattern.compile("([0-9]\\$|US\\$[0-9])");
 
 	// CheckStyle: ignore LineLength for next 4 lines
 	private static final Pattern VALID_CATEGORY_NAME_EN = Pattern.compile(CategoryValidation.NAME_EN_REGEXP);

src/test/groovy/ru/mystamps/web/feature/series/importing/SeriesInfoExtractorServiceImplTest.groovy

@@ -743,8 +743,9 @@ class SeriesInfoExtractorServiceImplTest extends Specification {
 		expect:
 			service.extractCurrency(fragment) == 'USD'
 		where:
-			fragment | _
-			'1,36$'  | _
+			fragment   | _
+			'1,36$'    | _
+			'US$16.50' | _
 	}
 
 }