keyTo: The foreign key used by the target model for this relation. keyFrom: The source key used by the source model for this relation.
E.g. when a Customer has many Order instances, then keyTo is “customerId”. Note that “customerId” is the default FK assumed by the framework, users can provide a custom FK name by setting “keyTo”. And Customer.id is keyFrom. keyFrom defaults to the id property of a model. Users can provide a custom source key name by setting “keyTo”.