fetchRelationData(relation, options) {
        const fromOptions = _.extend({}, options, {withRelated: [relation.from.relation]});

        const fromRelations = models[relation.from.model].findAll(fromOptions);
        const toRelations = models[relation.to.model].findAll(options);

        return Promise.all([fromRelations, toRelations]).then(([from, to]) => {
            return {
                from: from,
                to: to
            };
        });
    }
### Fetch Relation Data
Before we build relations we need to fetch all of the models from both sides so that we can
use filter and find to quickly locate the correct models.
@api private
@param {{from, to, entries}} relation
@returns {Promise<*>}