fix password generator requirement implementation for every configured character

src/main/java/PasswordGenerator.java

@@ -38,13 +38,13 @@ public class PasswordGenerator {
 
             if (isRequireEveryConfiguredCharacterType()) {
                 if (generatorPosition == 0 && isUseLowercase()) {
-                    customCharacterPool += lowercaseCharacters;
+                    customCharacterPool = lowercaseCharacters;
                 } else if (generatorPosition == 1 && isUseUppercase()) {
-                    customCharacterPool += uppercaseCharacters;
+                    customCharacterPool = uppercaseCharacters;
                 } else if (generatorPosition == 2 && isUseDigits()) {
-                    customCharacterPool += digits;
+                    customCharacterPool = digits;
                 } else if (generatorPosition == 3 && isUseSpecialCharacters()) {
-                    customCharacterPool += specialCharacters;
+                    customCharacterPool = specialCharacters;
                 } else {
                     customCharacterPool = characterPool;
                 }