code: public static <F> F mergeField(final F localValue, final F defaultValue) {
          return Optional.ofNullable(localValue).orElse(defaultValue);
      }
docs: Merges a (nullable) simple field on the local config object with a default (nullable) value in the default config object
  
  @param localValue   local field value
  @param defaultValue default field value
  @param <F>          the configuration object type
  @return the merged field value