TRIAGE: Support string and obj when return type is not known but client has to deserialize as T (?)

seems string or obj is not supported if the api client requires to deserialize as T, so maybe there should be some fallback strategy for it?

```fsharp

[]
type SomeType = { Test : string }

test_ce {
GETJ "/some/client/expecting/some-type" """{ "Test" : "hello" }"""
}
```

maybe this overload should work for GETJ_STR ?
```fsharp
GETJ_STR "/some/client/expecting/some-type" """{ "Test" : "hello" }""" // same as |> R_OK "application/json"
```