I saw the following error in Honeybadger:
```
[PROJECT_ROOT]/app/services/notifications/reactions/send.rb:61 :in `call`
old_json_data = notification.json_data
previous_siblings_size = notification.json_data["reaction"]["aggregated_siblings"].size if old_json_data
notification.json_data = json_data
[PROJECT_ROOT]/app/services/notifications/reactions/send.rb:20 :in `call`
[PROJECT_ROOT]/app/workers/notifications/new_reaction_worker.rb:16 :in `perform`
[PROJECT_ROOT]/app/models/notification.rb:84 :in `send_reaction_notification_without_delay`
[PROJECT_ROOT]/app/controllers/reactions_controller.rb:136 :in `destroy_reaction`
[PROJECT_ROOT]/app/controllers/reactions_controller.rb:168 :in `handle_existing_reaction`
[PROJECT_ROOT]/app/controllers/reactions_controller.rb:77 :in `create`
```
As I was exploring the error, I saw that we were making assumptions
about the data coercion. These are valid and somewhat stable
assumptions, but I wanted to look a little deeper into the situation.
This refactor helps consistently negotiate two situations where we're
transforming request-cycle models into lightweight data structures. It
also begins to show a path towards a generalizable "macro" for this behavior.
Related to #2122, #9534
24ccc5ac06