MM-45536: Track GraphQL queries in Grafana (#20609)

https://mattermost.atlassian.net/browse/MM-45536

```release-note
NONE
```

web/context.go

@@ -19,12 +19,15 @@ import (
 )
 
 type Context struct {
-	App           app.AppIface
-	AppContext    *request.Context
-	Logger        *mlog.Logger
-	Params        *Params
-	Err           *model.AppError
-	siteURLHeader string
+	App        app.AppIface
+	AppContext *request.Context
+	Logger     *mlog.Logger
+	Params     *Params
+	Err        *model.AppError
+	// This is used to track the graphQL query that's being executed,
+	// so that we can monitor the timings in Grafana.
+	GraphQLOperationName string
+	siteURLHeader        string
 }
 
 // LogAuditRec logs an audit record using default LevelAPI.