Error in your foreign key creations instructions page.

https://loopback.io/doc/en/lb4/todo-list-tutorial-sqldb.html#specify-the-foreign-key-constraints-in-todo-model
In your example below.

@model({
  settings: {
    foreignKeys: {
      fk_todo_todoListId: {
        name: 'fk_todo_todoListId',
        entity: 'TodoList',
        entityKey: 'id',
        foreignKey: 'todoListId',
      },
    },
  },
})
export class Todo extends Entity {
  //etc.
}

When following the setup above to run database migration for my local postgresdb as part of todo example tutorial, I encountered the following error:

Cannot migrate database schema error: column "todoListId" referenced in foreign key constraint does not exist
    at Parser.parseErrorMessage (/Users/andywongcheeming/Projects/poc/todo-list/node_modules/pg-protocol/dist/parser.js:283:98)

I was left puzzled why the instructions did not work as expected. I dig up online and my personal ChatGPT to understand if Postgres DB has case-sensitive when comes to table and field naming conventions. It turns out that it does.

When I go back and check my local postgres todo definitions via psql cli.

todo_db=# \d todo
                  Table "public.todo"
   Column   |  Type   | Collation | Nullable | Default
------------+---------+-----------+----------+---------
 id         | integer |           | not null |
 title      | text    |           | not null |
 desc       | text    |           |          |
 iscomplete | boolean |           |          |
 todolistid | integer |           |          |

It turns our the foreign key todolistid comes out as lower case by default when running Loopback db migration tool. The sample @model code above supplied as {foreignKey: 'todoListId'}.

I corrected it to use lower-case, dropped the database and started the migration all over again. The migration works this time.

Thus, I must ask - shouldn't the instructions be updated to use lowercase since the plugin creates tables and field names in lowercase by default?

Comienza por la sección sobre claves foráneas enlazada en el tutorial de base de datos SQL de la lista Todo de LoopBack y compara su valor foreignKey con el esquema de PostgreSQL producido por la migración. Actualiza el ejemplo para que la restricción documentada coincida con el nombre de columna generado y, después, verifica que el ejemplo Todo se migre correctamente contra PostgreSQL.