Refactor phpstan errors.

app/Models/AccountMeta.php

@@ -78,19 +78,17 @@ class AccountMeta extends Model
     /**
      * @param mixed $value
      *
-     * @return mixed
+     * @return string
      */
-    public function getDataAttribute($value): string
+    public function getDataAttribute(mixed $value): string
     {
         return (string)json_decode($value, true);
     }
 
     /**
      * @param mixed $value
-     *
-
      */
-    public function setDataAttribute($value): void
+    public function setDataAttribute(mixed $value): void
     {
         $this->attributes['data'] = json_encode($value);
     }

app/Models/PiggyBank.php

@@ -30,6 +30,7 @@ use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
 use Illuminate\Database\Eloquent\Relations\MorphMany;
+use Illuminate\Database\Eloquent\Relations\MorphToMany;
 use Illuminate\Database\Eloquent\SoftDeletes;
 use Illuminate\Database\Query\Builder;
 use Illuminate\Support\Carbon;
@@ -145,7 +146,7 @@ class PiggyBank extends Model
     }
 
     /**
-     * Get all of the piggy bank's notes.
+     * Get all the piggy bank's notes.
      */
     public function notes(): MorphMany
     {
@@ -155,7 +156,7 @@ class PiggyBank extends Model
     /**
      * Get all the tags for the post.
      */
-    public function objectGroups()
+    public function objectGroups(): MorphToMany
     {
         return $this->morphToMany(ObjectGroup::class, 'object_groupable');
     }