code: function getExplicitFieldReplacement(key, data) {
    if (!key.startsWith(FIELD_PREFIX)) {
      return;
    }
    const fieldName = key.substring(FIELD_PREFIX.length);
    return data.get(fieldName, '');
  }
docs: Allow `fields.` prefix in placeholder to override built in replacements like "slug" and "year" with values from fields of the same name.