Add Configurable Scout Key Type

[geisi]

Hello,

this PR improves the Scout integration when using custom keys for Searchable Models.

Problem

This problem was already addressed in the following issue:
#741

In one of our applications, we use incrementing IDs as the primary key for our models. Additionally, we are using the HasUuids trait to add a uuid column on top of the incrementing id. We did that because we didn't want to expose our incrementing IDs to the front end (and the search engine) due to security concerns.

We have done that by modifying the `getScouteKey' method.

    public function getScoutKey(): string
    {
        return $this->uuid;
    }

So far, so good indexing of these models works. But when we want to use the Model::search()->get() method within the query builder, we get a database exception because Scout thinks our primary key is an integer.

This happens within the queryScoutModelsByIds method. The scout package determines the used key type (integer or string) via the Eloquent getKeyType() method. This behavior is not correct in this case. When you can define a custom Scout key column, you should also be able to define the column type of this custom key.

Workaround

Before this PR, The workaround for this problem is to override the queryScoutModelsByIds() method within the models so the builder is doing a whereIn() instead of a whereIntegerRaw() condition.

Solution

I have added a new getScoutKeyType(): string method, which, by default, returns the model key type. This new method allows you to customize the key type Scout uses for querying models.

This should not be a breaking change since it does not change the default behavior of Scout, but it adds a little more flexibility in how custom key types can be used in Scout. There is a minor risk of naming collisions, but since the new method is prefixed with the scout word, it should be no problem.

[driesvints]

Hey @mmachatschek, does this change look okay to you?

[geisi]

I think if this PR gets merged, we should also create a PR for the Docs:

By default, Scout will use the primary key of the model as the model's unique ID / key that is stored in the search index. If you need to customize this behavior, you may override the getScoutKey, getScoutKeyName and getScoutKeyType methods on the model:

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;
use Laravel\Scout\Searchable;

class User extends Model
{
    use Searchable;

    /**
     * Get the value used to index the model.
     */
    public function getScoutKey(): mixed
    {
        return $this->email;
    }

    /**
     * Get the key name used to index the model.
     */
    public function getScoutKeyName(): mixed
    {
        return 'email';
    }

    /**
     * Get the auto-incrementing key type for querying models.
     *
     * @return string
     */
    public function getScoutKeyType()
    {
        return 'string';
    }

This current example in the docs won't work with Model::search() when you use incrementing IDs as the model's primary key.

[mmachatschek]

@driesvints @geisi the changes look good to me, even though I would prefer if we could add a test for this as well.

[geisi]

@mmachatschek Yes, you are right.

In the current test suite, I did not find any tests for the currently existing behavior, so I have not added some.

But I can create tests for the whole scoutKey logic.

[mmachatschek]

@geisi yes that would be great

[geisi]

@mmachatschek Tests are done (at least) for the new logic