External REST API Authentication via URL returned via DashBoard Webcomponent

I'm building an integration that uses an OAuth 2.0 endpoint to return an access token for a 3rd-Party REST API service. I'm unlikely to be able to get a client-credentials grant for machine-to-machine RSET interactions (which would be ideal, so I have to proceed this way). It's Xero (don't ask....)

The authentication endpoint uses a user/password followed by 2FA challenge in order to allow the API scope to be set, and an access token (and refresh token) to be returned to a redirect URL.

I can do this easily in PostMan because PostMan - whilst not having a valid redirect URL - can intercept the request and extract the information in the URL/response Headers sufficiently for them to be used in subsequent API Requests.

I'd rather not do this in PostMan going forward, and I'd like to handle the login/challenge in a Web Component in a Dashboard.

I can get as far as opening the login Web Page, completing the 2FA challenge and then authorising the scope of source Entities, BUT when I hit OK to return the access token (a JWT response), since there is no vaild redirect URL I can point to in the OneStream environment then I cannot get the JWT back within OneStream.

My questions therefore are:

• Is there any way I can get a redirect URL within the OneStream SaaS environment (I could probably do it if we were on-premise as I'd just pop something in IIS to handle it)?
• If I can't get a working redirect URL, then is there any way that I can capture the response to the interactions in the Web Component (all I can access is the URL that is opened by the component)

Thanks

Steve