hasMany = function hasMany(related, opts) {
  return function (mapper) {
    Relation.hasMany(related, opts).assignTo(mapper);
  };
}
HasMany relation decorator. You probably won't use this directly.

@name module:js-data.hasMany
@method
@param {Mapper} related The relation of which the target has many.
@param {object} opts Configuration options.
@param {string} [opts.foreignKey] The field that holds the primary key of the
related record.
@param {string} opts.localField The field that holds a reference to the
related record object.
@returns {Function} Invocation function, which accepts the target as the only
parameter.