Django. Custom views for admin.

admin.py

@admin.register(Order)
class OrderAdmin(admin.ModelAdmin):
    list_display = [
        'name',
        'status',
        'add_product_action', 
        'add_mattress_action'
    ]
    list_display_links = ['name', 'status']
    readonly_fields = [
        'add_product_action',
        'add_mattress_action',
    ]
    search_fields = ['name']

    def get_urls(self):
        urls = super().get_urls()
        custom_urls = [
            url(
                r'^(?P<order_id>.+)/add_matress/$',
                self.admin_site.admin_view(self.add_mattress_view),
                name='add_mattress_to_order',
            ),
            url(
                r'^(?P<order_id>.+)/add_product/$',
                self.admin_site.admin_view(self.add_product_view),
                name='add_product_to_order',
            ),
        ]
        return custom_urls + urls

    def add_product_action(self, obj):
        return format_html(
            '<a class="button" href="{}">{}</a>',
            reverse('admin:add_product_to_order', args=[obj.pk]),
            _("Add product")
        )
    add_product_action.short_description = _('Add product')
    add_product_action.allow_tags = True

    def add_mattress_action(self, obj):
        return format_html(
            '<a class="button" href="{}">{}</a>',
            reverse('admin:add_mattress_to_order', args=[obj.pk]),
            _("Add mattress")
        )
    add_mattress_action.short_description = _('Add mattress')
    add_mattress_action.allow_tags = True

    def add_mattress_view(self, request, order_id, **kwargs):
        order = self.get_object(request, order_id)
        if request.method != 'POST':
            form = AddMattressToOrderForm()
        else:
            form = AddMattressToOrderForm(request.POST)
            if form.is_valid():
                form.save(order)
                self.message_user(request, _('Success. Mattress was added to order.'))
                url = reverse(
                    'admin:orders_order_change',
                    args=[order_id],
                    current_app=self.admin_site.name,
                )
                return HttpResponseRedirect(url)
        context = self.admin_site.each_context(request)
        context['opts'] = self.model._meta
        context['form'] = form
        context['title'] = _('Add mattress to order')
        return TemplateResponse(
            request,
            'admin/custom_action_form.html',
            context,
        )

    def add_product_view(self, request, order_id, **kwargs):
        order = self.get_object(request, order_id)
        if request.method != 'POST':
            form = AddProductToOrderForm()
        else:
            form = AddProductToOrderForm(request.POST)
            if form.is_valid():
                form.save(order)
                self.message_user(request, _('Success. Mattress was product to order.'))
                url = reverse(
                    'admin:orders_order_change',
                    args=[order_id],
                    current_app=self.admin_site.name,
                )
                return HttpResponseRedirect(url)
        context = self.admin_site.each_context(request)
        context['opts'] = self.model._meta
        context['form'] = form
        context['title'] = _('Add product to order')
        return TemplateResponse(
            request,
            'admin/custom_action_form.html',
            context,
        )

custom_action_form.html

{% extends "admin/change_form.html" %}
{% load i18n admin_static admin_modify %}
{% block content %}
<div id="content-main">
  <form action="" method="POST">
    {% csrf_token %}
    {% if form.non_field_errors|length > 0 %}
      <p class="errornote">
          "Please correct the errors below."
      </p>
      {{ form.non_field_errors }}
    {% endif %}
    <fieldset class="module aligned">
      {% for field in form %}
        <div class="form-row">
          {{ field.errors }}
          {{ field.label_tag }}
          {{ field }}
          {% if field.field.help_text %}
          <p class="help">
            {{ field.field.help_text|safe }}
          </p>
          {% endif %}
        </div>
      {% endfor %}
    </fieldset>
    <div class="submit-row">
      <input type="submit" class="default" value="Submit">
    </div>
  </form>
</div>
{% endblock %}

forms.py

from decimal import Decimal

from django import forms
from django.forms import ModelChoiceField

from apps.mattress.models import MattressSizePrice
from apps.orders.const import BLOCK_READY
from apps.orders.models import OrderProducts, MattressInWork, OrderMattress
from apps.products.models import ProductSizePrice

__all__ = (
    'AddMattressToOrderForm',
    'AddProductToOrderForm',
    'MattressInWorkAdminForm'
)


class AddMattressToOrderForm(forms.Form):
    size_mattress = ModelChoiceField(
        queryset=MattressSizePrice.objects.all(),
        required=True
    )

    def save(self, order):
        order_mattress = OrderMattress.objects.create(
            order=order,
            mattress_size=self.cleaned_data['size_mattress'],
            build=self.cleaned_data['size_mattress'].mattress.build,
            price=Decimal(self.cleaned_data['size_mattress'].price)
        )
        return order_mattress


class AddProductToOrderForm(forms.Form):
    size_product = ModelChoiceField(
        queryset=ProductSizePrice.objects.all(),
        required=True
    )

    def save(self, order):
        order_product = OrderProducts.objects.create(
            order=order,
            product_size=self.cleaned_data['size_product'],
            price=Decimal(self.cleaned_data['size_product'].price)
        )
        return order_product