Add support for ThroughOptions #122
Description
See http://docs.sequelizejs.com/manual/tutorial/associations.html#n-m
Post.belongsToMany(Tag, { through: { model: ItemTag, unique: false, scope: { taggable: 'post' } }, foreignKey: 'taggable_id', constraints: false });and https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/sequelize/index.d.ts#L1374:
interface ThroughOptions { /** * The model used to join both sides of the N:M association. */ model: Model<any, any>; /** * A key/value set that will be used for association create and find defaults on the through model. * (Remember to add the attributes to the through model) */ scope?: AssociationScope; /** * If true a unique key will be generated from the foreign keys used (might want to turn this off and create * specific unique keys when using scopes) * * Defaults to true */ unique?: boolean; }