[.NET] Allow for System.Text.Json types in HTTP Trigger Binding

[brandonh-msft]

What problem would the feature you're requesting solve? Please describe.

I tried to use System.Text.Json.JsonDocument as the binding type for HttpTrigger in in-proc Functions v4 (.NET 6) and was met with a serialization error ("no default constructor"). As we support Newtonsoft.Json types here (e.g. JObject), we should also support STJ types.

Describe the solution you'd like

Allow for, at minimum, System.Text.Json.JsonDocument support.

Describe alternatives you've considered

One can, of course, use HttpRequest and manually .Parse() the content of it, but that's always been possible and shouldn't be an excuse for not supporting our own JSON object model as a serialization target (as this "workaround" could similarly argue that no types outside HttpRequest should be implemented).

[jviau]

I don't believe we have any plans to invest in adding STJ support to in-proc.

@fabiocav, @brettsam for additional comment.

[aishwaryabh]

No plans to add STJ support to in proc