public CustomFieldMappings mergeWith(final CustomFieldMapping changedMapping) {
        final Set<CustomFieldMapping> modifiedMappings = new HashSet<>(this);
        modifiedMappings.removeIf(m -> changedMapping.fieldName().equals(m.fieldName()));
        modifiedMappings.add(changedMapping);
        return new CustomFieldMappings(modifiedMappings);
    }
@Test
    void testReturnsOriginalMappingsIfMergedWithNullMappings() {
        CustomFieldMappings customFieldMappings = new CustomFieldMappings(List.of());
        assertSame(customFieldMappings, customFieldMappings.mergeWith((CustomFieldMappings) null));
    }