Ring-out as another extension from a service user

Hi,

I have an App used to authenticate through OAuth with a service user as the goal is to have customers authenticating just once. I'm working with the Ring-Out API to initiate calls on behalf of users from our application, and it works as far as the correct "from" phone number is provided to a given extension, however, it seems wrong in "Call Log" as the calls originating extension is actually the one from the service user.

A detailed explanation of the use case:

A single user from a RingCentral account is used as a service user to authenticate via OAuth and grant access to the RingCentral's APIs;
Ring-Out calls are originated from a third-party application through the authenticated user. Let's say "User A" is the one connected, and a call should be initiated to "User B".

Expectation:

It'd be expected to have the call logged against the extension of "User B", not "User A"

Current behavior:

The call is getting logged against the extension of "User A"

A screenshot from "Call Log":

I'm using RingCentral's JS SDK to interact with the API, see below a piece of the code:

platform.post(`/restapi/v1.0/account/~/extension/~/ring-out`, ringOutOpts)

I've tried to use the "extensionId" of "User B" a part of the URL but when I do so I get the following error:

Resource for parameter [extensionId] is not found

Is it possible to achieve what I'm trying here? If so, what am I doing wrong?

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