Add MorphTo relation populator

src/Populator.php

@@ -10,6 +10,7 @@
 use Greabock\Populator\Relation\MorphManyPopulator;
 use Greabock\Populator\Relation\MorphOnePopulator;
 use Greabock\Populator\Relation\MorphToManyPopulator;
+use Greabock\Populator\Relation\MorphToPopulator;
 use Greabock\Populator\Relation\RelationPopulator;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
@@ -18,6 +19,7 @@
 use Illuminate\Database\Eloquent\Relations\HasOne;
 use Illuminate\Database\Eloquent\Relations\MorphMany;
 use Illuminate\Database\Eloquent\Relations\MorphOne;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
 use Illuminate\Database\Eloquent\Relations\MorphToMany;
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Support\Arr;
@@ -143,6 +145,7 @@ protected function populateRelation(Model $model, string $relationName, ?array $
     private function initRelationPopulators(): void
     {
         $this->relationPopulators = [
+            MorphTo::class       => new MorphToPopulator($this->resolver, $this->uow, $this),
             HasMany::class       => new HasManyPopulator($this->resolver, $this->uow, $this),
             BelongsToMany::class => new BelongsToManyPopulator($this->resolver, $this->uow, $this),
             BelongsTo::class     => new BelongsToPopulator($this->resolver, $this->uow, $this),

src/Relation/MorphToPopulator.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Greabock\Populator\Relation;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+use Illuminate\Database\Eloquent\Relations\MorphTo;
+use Illuminate\Database\Eloquent\Relations\Relation;
+use Illuminate\Support\Str;
+
+class MorphToPopulator extends RelationPopulator
+{
+    /**
+     * @param Model $model
+     * @param Relation|MorphTo $relation
+     * @param array|null $data
+     * @param string $relationName
+     * @throws \Exception
+     */
+    function populate(Model $model, Relation $relation, ?array $data, string $relationName): void
+    {
+        $related = $this->populator->populate(get_class($relation->getRelated()), $data);
+
+        $this->fillRelationField($model, $relation, $related);
+
+        $model->setRelation(Str::snake($relation->getRelationName()), $related);
+    }
+
+    protected function fillRelationField(Model $model, BelongsTo $relation, ?Model $related): void
+    {
+        $model->{$relation->getForeignKeyName()} = $related ? $related->{$relation->getOwnerKeyName()} : null;
+    }
+}