Add a new test for `report.extension_data`

[DrChat]

Summary of the Pull Request

Adds a new (failing) test for using report.extension_data in a notification template.

PR Checklist

• [ ] Applies to work item: #3485
• [ ] CLA signed. If not, go over here and sign the CLI.
• [ ] Tests added/passed
• [ ] Requires documentation to be updated
• [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

[DrChat]

Looks like this is going to be a massive PITA to fix. Basically, Scriban doesn't support JsonElement in any capacity for their little ScriptObject helper. So we can't pass JsonElement in any capacity to them. Additionally, ScriptObject.Import supports filtering and renaming fields, but not converting them :\

It looks like Newtonsoft.Json may be a better choice for deserializing JSON, as they have full support for converting JSON to arbitrary C# objects (dynamic) instead of just JsonElement (reference)

I've also found this solution for using System.Text.Json to convert arbitrary JSON to a tree of dynamic objects: https://dotnetfiddle.net/1Y6hI6

See here for more context: https://github.com/scriban/scriban/issues/148