getOauthAccessToken
Obtains an OAuth2 access token for use with consent-based API endpoints.
Always uses the CIBA grant (grant_type=urn:openid:params:grant-type:ciba), which requires a valid auth_req_id from a prior bcAuthorize call. Passing a blank backChannelAuthorizationRequestId is a programming error: the method emits NetworkResult.Error immediately rather than forwarding an invalid request to the server.
Return
A Flow emitting NetworkResult.Error immediately if backChannelAuthorizationRequestId is blank, otherwise emitting NetworkResult.Loading then a terminal NetworkResult.Success or NetworkResult.Error from the network call.
Parameters
The type of product for which to obtain the OAuth2 access token.
The subscription key for the product.
The auth_req_id returned by a prior bcAuthorize call. Must not be blank.