'date', 'payment_date' => 'date', 'quantity' => 'integer', 'unit_price' => 'integer', 'total_amount' => 'integer', 'paid_amount' => 'integer', 'is_paid' => 'boolean', ]; } public function customer(): BelongsTo { return $this->belongsTo(Customer::class); } public function unit(): BelongsTo { return $this->belongsTo(Unit::class); } }