Resolve "Apps should be able to register URLs for API stuff which are not mounted under /django/"

Closes #808 (closed)

aleksis/core/urls.py

+from importlib import import_module
+
 from django.apps import apps
 from django.conf import settings
 from django.contrib import admin
@@ -410,10 +412,18 @@ for app_config in apps.app_configs.values():
         continue
 
     try:
-        urlpatterns.append(
-            path(f"django/app/{app_config.label}/", include(f"{app_config.name}.urls"))
-        )
-    except ModuleNotFoundError:
+        urls_module = import_module(f"{app_config.name}.urls")
+
+        if hasattr(urls_module, "urlpatterns"):
+            urlpatterns.append(
+                path(f"django/app/{app_config.label}/", include(urls_module.urlpatterns))
+            )
+
+        if hasattr(urls_module, "api_urlpatterns"):
+            urlpatterns.append(
+                path(f"app/{app_config.label}/", include(urls_module.api_urlpatterns))
+            )
+    except ImportError:
         # Ignore exception as app just has no URLs
         pass  # noqa