Case insensitive keys for relation models

What steps will reproduce the problem?

 $dataProvider = new ActiveDataProvider([
            'query' => $query->joinWith(['someCaseInsensitiveRelation']),
        ]);

What is the expected result?

So If I make request without dataProvider, I have got all related models:

What do you get instead?

but if I using dataProvider related models will be empty

Additional info

It's happens because model keys case sensitive. For example I using Postgres citext or for MySQL (for utf8) my on condition case insensitive (luke = Luke).

I suggest add optional feature for this. May be useCaseInsensitiveKeys = false or something else? It might looks like:

//vendor/yiisoft/yii2/db/ActiveRelationTrait.php

    private function normalizeModelKey($value)
    {
        if (is_object($value) && method_exists($value, '__toString')) {
            // ensure matching to special objects, which are convertable to string, for cross-DBMS relations, for example: `|MongoId`
            $value = $value->__toString();
        }

        return $this->useCaseInsensitiveKeys ? strtolower($value) : $value;
    }

any suggestions?

related to #9077

Start in vendor/yiisoft/yii2/db/ActiveRelationTrait.php and reproduce the difference between joinWith('someCaseInsensitiveRelation') through ActiveDataProvider and a direct request. Compare how relation model keys are matched for PostgreSQL citext and case-insensitive MySQL conditions. Done means related models are populated when keys differ only by case, with the opt-in behavior and API agreed.