cmc-sales/cmc-django/cmcsales/cmc/templates/partials/customer_list.html

{% for customer in customers %}
    <option value="{{ customer.id }}" hx-get="{% url 'load_contacts' %}?customer_id={{ customer.id }}" hx-target="#contact-select" hx-trigger="click">
        {{ customer.name }}
    </option>
{% endfor %}