shouldIncludeLinkageData(relationshipKey, model) {
    return false;
  }
Allows for per-relationship inclusion of linkage data. Use this when `alwaysIncludeLinkageData` is not granular enough.

    ```js
    export default JSONAPISerializer.extend({
      shouldIncludeLinkageData(relationshipKey, model) {
        if (relationshipKey === 'author' || relationshipKey === 'ghostWriter') {
          return true;
        }
        return false;
      }
    });
    ```

    @method shouldIncludeLinkageData
    @param {String} relationshipKey
    @param {Model} model
    @return {Boolean}
    @public