async addFixturesForRelation(relationFixture, options) {
        const ops = [];
        let max = 0;

        const data = await this.fetchRelationData(relationFixture, options);

        _.each(relationFixture.entries, (entry, key) => {
            const fromItem = data.from.find(FixtureManager.matchFunc(relationFixture.from.match, key));

            // CASE: You add new fixtures e.g. a new role in a new release.
            // As soon as an **older** migration script wants to add permissions for any resource, it iterates over the
            // permissions for each role. But if the role does not exist yet, it won't find the matching db entry and breaks.
            if (!fromItem) {
                logging.warn('Skip: Target database entry not found for key: ' + key);
                return Promise.resolve();
            }

            _.each(entry, (value, entryKey) => {
                let toItems = data.to.filter(FixtureManager.matchFunc(relationFixture.to.match, entryKey, value));
                max += toItems.length;

                // Remove any duplicates that already exist in the collection
                toItems = _.reject(toItems, (item) => {
                    return fromItem
                        .related(relationFixture.from.relation)
                        .find((model) => {
                            const objectToMatch = FixtureManager.matchObj(relationFixture.to.match, item);
                            return Object.keys(objectToMatch).every((keyToCheck) => {
                                return model.get(keyToCheck) === objectToMatch[keyToCheck];
                            });
                        });
                });

                if (toItems && toItems.length > 0) {
                    ops.push(function addRelationItems() {
                        return baseUtils.attach(
                            models[relationFixture.from.Model || relationFixture.from.model],
                            fromItem.id,
                            relationFixture.from.relation,
                            toItems,
                            options
                        );
                    });
                }
            });
        });

        const result = await sequence(ops);
        return {expected: max, done: _(result).map('length').sum()};
    }
## Add Fixtures for Relation
Takes a relation fixtures object, with a from, to and some entries and processes these
into a sequence of promises, to get each fixture added.

@param {{from, to, entries}} relationFixture
@returns {Promise<any>}