[6.x] Change DatabaseNotification keyType to match uuid

[kendugu]

The default primary key for database notifications is a UUID, but the default keyType (from the base model) is an int. This causes ids with string UUIDs to be force cast as integers in MorphTo and other relationships.

framework/src/Illuminate/Database/Eloquent/Relations/Relation.php

Lines 310 to 323 in f5c3c60

	/**
	* Get the name of the "where in" method for eager loading.
	*
	* @param \Illuminate\Database\Eloquent\Model $model
	* @param string $key
	* @return string
	*/
	protected function whereInMethod(Model $model, $key)
	{
	return $model->getKeyName() === last(explode('.', $key))
	&& in_array($model->getKeyType(), ['int', 'integer'])
	? 'whereIntegerInRaw'
	: 'whereIn';
	}