Fix exists rule for foreign key column indicating table name

[nicodevs]

Issue Description

On a clean installation, a foreign key column specifying the name of the related table generates an incorrect exists rule in the form request. For instance, the following YAML:

models:
  Message:
    subject: string
    sender_id: id foreign:users
controllers:
  Message:
    resource: api

... generates these rules in MessageStoreRequest and MessageUpdateRequest:

    public function rules(): array
    {
        return [
            'subject' => ['required', 'string'],
            'sender_id' => ['required', 'integer', 'exists:senders,id'],
        ];
    }

The expected rule for sender_id should be:

-'sender_id' => ['required', 'integer', 'exists:senders,id'],
+'sender_id' => ['required', 'integer', 'exists:users,id'],

Solution

This PR updates the Rules translator to verify if the column includes a foreign table modifier and applies it in the exists rule when present. A test has been added to ensure this behavior.

Please let me know if the code and test look good and matches the coding style. Thanks!

[jasonmccreary]

Thanks.