Add graphql_request_context context manager to allow hooks around gra…

…phql request handling (#23373)

## Summary & Motivation

This allows subclasses to override the `graphql_request_context()`
method and inject code around the graphql handler. Specifically this
code runs in the same thread as the graphph resolver.

## How I Tested These Changes
Existing tests should be sufficient, since we're not changing any
behavior.

python_modules/dagster-webserver/dagster_webserver/graphql.py

@@ -1,5 +1,6 @@
 from abc import ABC, abstractmethod
 from asyncio import Task, get_event_loop, run
+from contextlib import contextmanager
 from enum import Enum
 from typing import (
     TYPE_CHECKING,
@@ -241,18 +242,24 @@ async def execute_graphql_request(
         request_context = self.make_request_context(request)
 
         def _graphql_request():
-            return run(
-                self._graphql_schema.execute_async(
-                    query,
-                    variables=variables,
-                    operation_name=operation_name,
-                    context=request_context,
-                    middleware=self._graphql_middleware,
+            with self.graphql_request_context(request):
+                return run(
+                    self._graphql_schema.execute_async(
+                        query,
+                        variables=variables,
+                        operation_name=operation_name,
+                        context=request_context,
+                        middleware=self._graphql_middleware,
+                    )
                 )
-            )
 
         return await run_in_threadpool(_graphql_request)
 
+    @contextmanager
+    def graphql_request_context(self, request: Request):
+        """This context manager executes within the threadpool and can be used to wrap logic around a single graphql request."""
+        yield
+
     async def execute_graphql_subscription(
         self,
         websocket: WebSocket,