django.core.files.storage: Improvements (#243)

- `Storage`: `url()` only accepts a string as a parameter.
- `default_storage`: instance of `Storage` as far as usage is concerned.

django-stubs/core/files/storage.pyi

@@ -17,7 +17,7 @@ class Storage:
     def exists(self, name: str) -> bool: ...
     def listdir(self, path: str) -> tuple[list[str], list[str]]: ...
     def size(self, name: str) -> int: ...
-    def url(self, name: str | None) -> str: ...
+    def url(self, name: str) -> str: ...
     def get_accessed_time(self, name: str) -> datetime: ...
     def get_created_time(self, name: str) -> datetime: ...
     def get_modified_time(self, name: str) -> datetime: ...
@@ -44,6 +44,6 @@ class FileSystemStorage(Storage):
 
 class DefaultStorage(LazyObject): ...
 
-default_storage: Any
+default_storage: Storage
 
 def get_storage_class(import_path: str | None = ...) -> type[Storage]: ...