fix: django length_is migration (#442)

Author: lukasvinclav

src/unfold/templates/admin/edit_inline/tabular.html

@@ -16,7 +16,7 @@ <h2 class="bg-gray-100 border border-transparent font-semibold mb-6 px-4 py-3 ro
             {{ inline_admin_formset.formset.non_form_errors }}
 
             <div>
-                {% if not inline_admin_formset.has_add_permission and inline_admin_formset.forms|length_is:0 %}
+                {% if not inline_admin_formset.has_add_permission and inline_admin_formset.forms|length == 0 %}
                     <p class="mb-6 text-gray-500 text-sm dark:text-gray-400">
                         {% trans "No records found." %}
                     </p>

src/unfold/templates/admin/includes/fieldset.html

@@ -15,9 +15,9 @@ <h2 class="bg-gray-100 border border-transparent font-semibold mb-6 px-4 py-3 ro
 
     <div class="aligned mb-8 {% if not stacked %}border border-gray-200 rounded-md pt-3 px-3 shadow-sm dark:border-gray-800{% endif %}">
         {% for line in fieldset %}
-            <div class="form-row block {% if not line.fields|length_is:'1' %}flex flex-row flex-wrap gap-x-8{% endif %}{% if not line.has_visible_field %} hidden{% endif %}{% for field in line %}{% if field.field.name %} field-{{ field.field.name }}{% endif %}{% endfor %}">
+            <div class="form-row block {% if not line.fields|length == 1 %}flex flex-row flex-wrap gap-x-8{% endif %}{% if not line.has_visible_field %} hidden{% endif %}{% for field in line %}{% if field.field.name %} field-{{ field.field.name }}{% endif %}{% endfor %}">
                 {% for field in line %}
-                    <div class="flex group {% if field.errors %}errors {% endif %}{% if not line.fields|length_is:1 %}lg:max-w-xs w-full {% endif %}{% if not forloop.parentloop.last %} mb-6 {% else %} mb-3{% endif %} {% if row %}flex-row items-center{% else %}flex-col{% endif %}">
+                    <div class="flex group {% if field.errors %}errors {% endif %}{% if not line.fields|length == 1 %}lg:max-w-xs w-full {% endif %}{% if not forloop.parentloop.last %} mb-6 {% else %} mb-3{% endif %} {% if row %}flex-row items-center{% else %}flex-col{% endif %}">
                         {% if field.is_checkbox %}
                             <div class="flex flex-row items-center">
                                 {{ field.field }}{{ field.label_tag }}