Add descriptive subheader for listing pages in django admin

src/registrar/admin.py

@@ -141,6 +141,26 @@ class DomainApplicationAdmin(AuditedAdmin):
             # Regular users can only view the specified fields
             return self.readonly_fields
         
+    def changelist_view(self, request, extra_context=None):
+        if extra_context is None:
+            extra_context = {}
+        # Get the filtered values
+        filters = self.get_filters(request)
+        # Pass the filtered values to the template context
+        extra_context['filters'] = filters
+        extra_context['search_query'] = request.GET.get('q', '')  # Assuming the search query parameter is 'q'
+        return super().changelist_view(request, extra_context=extra_context)
+
+    def get_filters(self, request):
+        filters = []
+        # Retrieve the filter parameters
+        for param in request.GET.keys():
+            # Exclude the default search parameter 'q'
+            if param != 'q' and param != 'o':
+                # Append the filter parameter and its value to the list
+                filters.append({'parameter_name': param.replace('__exact','').replace('_type','').replace('__id',' id'), 'parameter_value': request.GET.get(param)})
+        return filters
+
 
 admin.site.register(models.User, MyUserAdmin)
 admin.site.register(models.UserDomainRole, AuditedAdmin)

src/registrar/config/settings.py

@@ -78,6 +78,12 @@ DEBUG = env_debug
 # Installing them here makes them available for execution.
 # Do not access INSTALLED_APPS directly. Use `django.apps.apps` instead.
 INSTALLED_APPS = [
+    # let's be sure to install our own application!
+    # it needs to be listed before django.contrib.admin 
+    # otherwise Django would find the default template 
+    # provided by django.contrib.admin first and use 
+    # that instead of our custom templates.
+    "registrar",
     # Django automatic admin interface reads metadata
     # from database models to provide a quick, model-centric
     # interface where trusted users can manage content
@@ -106,8 +112,6 @@ INSTALLED_APPS = [
     "django_fsm",
     # library for phone numbers
     "phonenumber_field",
-    # let's be sure to install our own application!
-    "registrar",
     # Our internal API application
     "api",
     # Only for generating documentation, uncomment to run manage.py generate_puml

src/registrar/templates/admin/change_list.html

@@ -0,0 +1,22 @@
+{% extends "admin/change_list.html" %}
+
+{% block content_title %}
+    <h1>{{ title }}</h1>
+    <h2>
+        {{ cl.result_count }} 
+        {% if cl.get_ordering_field_columns %}
+            sorted
+        {% endif %}
+        results
+        {% if filters %}
+            filtered by
+                {% for filter_param in filters %}
+                    {{ filter_param.parameter_name }} = {{ filter_param.parameter_value }}
+                    {% if not forloop.last %}, {% endif %}
+                {% endfor %}
+        {% endif %}
+        {% if search_query  %}
+            for {{ search_query }}
+        {% endif %}
+    </h2>    
+{% endblock %}