Polymorphic Relation - Wrong Doc

Describe the bug

Hi there!

Let's suppose a base Delivery model with 3 fields: id, deliverableType, and deliverableId.
If you follow the docs, you'll get this error when requesting some deliverable relations:

Request GET /deliveries?filter=whatever failed with status code 500. Error: ER_BAD_FIELD_ERROR: Unknown column 'deliverable' in 'field list'

This is caused by this part of code, as you're asking it to search on the corresponding datasource for the field "deliverable" which doesn't exist:

class Delivery extends Entity {
@hasOne(() => Deliverable, {polymorphic: true})
  deliverable: Deliverable;

deliverableType: string;
}

Instead, it should be like this (search deliverableId on deliverableType's model):

class Delivery extends Entity {
@hasOne(() => Deliverable, {polymorphic: true})
  deliverableId: string;

deliverableType: string;
id: string;
}

With that change, polymorphic relation is working as expected (assuming repositories are correctly configured)

Logs

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Additional information

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Reproduction

Not needed

Commencez par la documentation de Polymorphic relation à l’adresse https://loopback.io/doc/en/lb4/Polymorphic-relation.html et comparez son exemple Delivery avec les champs signalés dans l’issue. Mettez à jour l’exemple afin que la relation utilise deliverableId et deliverableType, puis vérifiez que l’exemple documenté ne demande plus le champ inexistant deliverable.