Cannot migrate database schema error: The associated field "todoListId" in the foreign key constraint does not exist"

@achrinza is already working on this.

Since Jun 26, 2022.

### Describe the bug

## What is the problem
When I was doing code practice in the **Running on relational databases** section, running `npm run migrate` reported an error:
`Cannot migrate database schema error: The associated field "todoListId" in the foreign key constraint does not exist`,
## The connected DB
Consistent with tutorial - Postgre DB

## How I handle it
**Change the value of the foreignKey to full lowercase**
todo.model.ts
```
@model({
settings: {
postgresql: {
schema: 'lb4', // schema name
table: 'todo' // table name
},
foreignKeys: {
fk_todo_todoListId: {
name: 'fk_todo_todoListId',
entity: 'TodoList',
entityKey: 'id',
foreignKey: 'todolistid', // The value in the official tutorial is todoListId
},
}
}
})
export class Todo extends Entity {
// etc
}
```

## Suggestion
**Whether the code content should be changed in the tutorial**
**Transform**: foreignKey: 'todoListId' -> foreignKey: 'todolistid'

### Logs

_No response_

### Additional information

_No response_

### Reproduction

https://github.com/RokeyJoe/Loopback4-todo-list.git