Introduce new model for future remodeling of split transactions.

app/Models/TransactionJournal.php

@@ -186,6 +186,15 @@ class TransactionJournal extends Model
         return $this->belongsToMany(Category::class);
     }
 
+    /**
+     * @codeCoverageIgnore
+     * @return BelongsToMany
+     */
+    public function transactionGroups(): BelongsToMany
+    {
+        return $this->belongsToMany(Category::class);
+    }
+
     /**
      * @codeCoverageIgnore
      *