refactor: Use ActivityService to create system messages in seeder

app/Models/Mutation.php

@@ -20,6 +20,7 @@ class Mutation extends Model
         'amount',
         'description',
         'status',
+        'predefined_mutation_id',
     ];
 
     public function ledger(): BelongsTo
@@ -32,6 +33,11 @@ class Mutation extends Model
         return $this->belongsTo(User::class);
     }
 
+    public function predefinedMutation(): BelongsTo
+    {
+        return $this->belongsTo(PredefinedMutation::class);
+    }
+
     public function chat(): MorphOne
     {
         return $this->morphOne(Chat::class, 'chatable');