Error when adding team members to an initally created team folder via http endpoint

Hi Sdrawko, hi Greg,

@Sdrawko:
If you read my post carefully, I never meant that you're Russian 🙂 I just learned the cyrillic alphabet as side effect when learning Russian at school.
And, I know that some baltic countries (and maybe others) also use the cyrillic alphabet. But even in such country you have a chance to communicate using Russian. 
Anyway I've to sincerely apologize for the confusion.

Back to business:
I'm using HTTP endpoints only (using REST calls) so no "real" SDK will apply.
The programming language I use is called "ABAP Objects", which is SAP only.

Example:
Endpoint https://api.dropboxapi.com/2/sharing/add_folder_member

In order to add a user to that folder I have to use the "Dropbox-API-Select-Admin: <TEAM_MEMBER_ID>" header parameter as stated here:
https://www.dropbox.com/developers/documentation/http/documentation#sharing-add_folder_member

curl example using the admin authorization is here:
https://www.dropbox.com/developers/reference/auth-types#admin-authentication

curl -X POST "https://api.dropboxapi.com/2/users/get_current_account" \
--header "Authorization: Bearer <OAUTH2_ACCESS_TOKEN>" \
--header "Dropbox-API-Select-Admin: <TEAM_MEMBER_ID>"

I'm performing the following steps:
- create REST API class instance
- open http connection
- fetch new oauth2 token using my secret refresh token (refresh token was generated when authorizing the app the first time) and set header field
->http header field = "Authorization: Bearer <oauth2 token>"
- create header field for admin authorization
->http header field = "Dropbox-API-Select-Admin: dbmid<my team member id>"
- create "request" class instance
- set "Content-Type" to "application/json" via request class (this actually generates the corresponding "Content-Type" header parameter)
- build json string with info about new user, team folder etc.
- set json as request data
- make POST request
- create "response" class instance
- get server response & status
- evaluate response & status
- close http connection

All these steps work flawlessly making REST calls to other endpoints (without admin auth.).
Unfortunately there seems to be no useful example in the documentation making use of the "Dropbox-API-Select-Admin" parameter.
At least I wasn't able to find one.

So, please understand: I cannot see any reason why I'm getting this popup, since I DO send a Bearer token.
Here's the ABAP-Objects code with some comments:
...
IF lo_rest_client IS BOUND. "check if class instance has been created
"lo_auth is an instance of a class which handles oauth2 tokens
lo_auth->get_bearer_auth_name_value( IMPORTING es_bearer_auth = ls_auth_bearer ). "fetch new oauth2 token (or use last token if not expired)
IF ls_auth_bearer IS NOT INITIAL.
lo_rest_client->set_request_header( iv_name = ls_auth_bearer-name "Authorization
                                                             iv_value = ls_auth_bearer-value ). "Bearer <oauth2 token>
lo_rest_client->set_request_header( iv_name = /karon/cl_dropbox_co=>mc_dbx_par_api_select_admin "Dropbox-API-Select-Admin
                                                             iv_value = lv_dbx_team_admin ). "dbmid:<team member id>
lo_rest_client->set_request_header( iv_name = /karon/cl_dropbox_co=>mc_url_par_request_uri "~request_uri
                                                             iv_value = `/2/sharing/share_folder` ).
lo_request_entity = lo_rest_client->create_request_entity( ).
lo_request_entity->set_content_type( iv_media_type = /karon/cl_dropbox_co=>mc_content_json ). "application/json
lo_request_entity->set_string_data( iv_data = lv_json ). "json string with parameters
lo_rest_client->post( io_entity = lo_request_entity ).
...

The only reason why I'm sending a Basic token is as response of the authorization popup I'm constantly getting.
IMHO the question is not why I'm getting an error (which is pretty much clear), but why this popup appears.

REST calls to endpoints which require the "Dropbox-API-Select-User" parameter also work without a hitch.

Best regards,
Jan