request: Move miscellaneous attributes to ZulipRequestNotes.

This includes the migration of fields that require trivial changes
to be migrated to be stored with ZulipRequestNotes.

Specifically _requestor_for_logs, _set_language, _query, error_format,
placeholder_open_graph_description, saveed_response, which were all
previously set on the HttpRequest object at some point. This migration
allows them to be typed.

zerver/views/documentation.py

@@ -13,7 +13,7 @@ from django.views.generic import TemplateView
 from zerver.context_processors import zulip_default_context
 from zerver.decorator import add_google_analytics_context
 from zerver.lib.integrations import CATEGORIES, INTEGRATIONS, HubotIntegration, WebhookIntegration
-from zerver.lib.request import REQ, has_request_variables
+from zerver.lib.request import REQ, get_request_notes, has_request_variables
 from zerver.lib.subdomains import get_subdomain
 from zerver.lib.templates import render_markdown_path
 from zerver.models import Realm
@@ -168,10 +168,11 @@ class MarkdownDirectoryView(ApiURLView):
                 context["OPEN_GRAPH_TITLE"] = f"{article_title} ({title_base})"
             else:
                 context["OPEN_GRAPH_TITLE"] = title_base
-            self.request.placeholder_open_graph_description = (
+            request_notes = get_request_notes(self.request)
+            request_notes.placeholder_open_graph_description = (
                 f"REPLACMENT_OPEN_GRAPH_DESCRIPTION_{int(2**24 * random.random())}"
             )
-            context["OPEN_GRAPH_DESCRIPTION"] = self.request.placeholder_open_graph_description
+            context["OPEN_GRAPH_DESCRIPTION"] = request_notes.placeholder_open_graph_description
 
         context["sidebar_index"] = sidebar_index
         # An "article" might require the api_uri_context to be rendered