fix(core): Replace special characters with a post processing step (#78)

[nandorholozsnyak]

• Markup language related special characters are being replaced
• Domain specific classes got some rework

Closes #78

[Lindenson]

Please add this PostProcessor to the list:

    public PropertyGroupFilterService() {
        this(List.of(
            new UnknownGroupRemovalPostProcessor(),
            new IncludeExcludeGroupPostProcessor(),
            new IncludeExcludePropertyPostProcessor(),
            new EmptyGroupRemovalPostProcessor(),
            new UnknownGroupRenamePostProcessor(),
            new SpecialCharacterPostProcessor()
        ));
    }

Also this is not null safe (please change the code by adding if (Objects.nonNull...):

    private void replaceSpecialCharacters(Property property, Map<String, String> specialCharacterMap) {
        specialCharacterMap.forEach((character, replacement) -> {
            if (Objects.nonNull(property.getDescription()))
                property.setDescription(property.getDescription().replace(character, replacement));
            if (Objects.nonNull(property.getDefaultValue())) 
                property.setDefaultValue(property.getDefaultValue().replace(character, replacement));
        });
    }

[nandorholozsnyak]

Thank you @Lindenson for the comment. I'll be finishing this PR soon.