common: add new 'common' app for custom middleware

- new middleware was required for setting cache-control headers without
  impacting server-side cache
- this middleware is potenially cross-cutting
- settings requires modules to exist in an app

TWLight/common/__init__.py

@@ -0,0 +1 @@
+

TWLight/common/apps.py

@@ -0,0 +1,9 @@
+from django.apps import AppConfig
+
+
+class MiddlewareConfig(AppConfig):
+    name = "TWLight.common"
+    label = "common"
+
+    def ready(self):
+        import TWLight.common.middleware

TWLight/common/middleware/__init__.py

@@ -0,0 +1 @@
+

TWLight/common/middleware/cache.py

@@ -0,0 +1,17 @@
+from django.conf import settings
+from django.utils.cache import add_never_cache_headers
+
+
+class NeverCacheHttpHeadersMiddleware:
+    """
+    Callable middleware that sets cache-control headers without impacting server-side caching
+    """
+
+    def __init__(self, get_response):
+        self.get_response = get_response
+
+    def __call__(self, request):
+        response = self.get_response(request)
+        if request.path in settings.NEVER_CACHE_HTTP_HEADER_PATHS:
+            add_never_cache_headers(response)
+        return response

TWLight/settings/base.py

@@ -48,6 +48,11 @@
     }
 }
 
+# Site paths that shouldn't be cached browser-side
+NEVER_CACHE_HTTP_HEADER_PATHS = [
+    "/users/my_library/",
+]
+
 # An atypical way of setting django languages for TranslateWiki integration:
 # https://translatewiki.net/wiki/Thread:Support/_The_following_issue_is_unconfirmed,_still_to_be_investigated._Adding_TheWikipediaLibrary_Card_Platform_TranslateWiki
 
@@ -129,6 +134,7 @@ def get_django_faker_languages_intersection(languages):
     "TWLight.comments",
     "TWLight.api",
     "TWLight.ezproxy",
+    "TWLight.common",
 ]
 
 # dal (autocomplete_light) must go before django.contrib.admin.
@@ -171,6 +177,7 @@ def get_django_faker_languages_intersection(languages):
     # That’s why SessionMiddleware must be enabled and appear before
     # MessageMiddleware.
     "django.contrib.messages.middleware.MessageMiddleware",
+    "TWLight.common.middleware.cache.NeverCacheHttpHeadersMiddleware",
 ]