Probleme

I want to create a server application that modifies playlists on spotify, deezer and youtube (to create multi-platform playlists). My problem is that these different services require OAuth2 authentication to manipulate playlists, and that this authentication requires human intervention

What I've tried

I tried to use the api key, but it did not allow me to edit the playlist (access_key needed).

My Research

from what I understood from the different documentation, the api key is made for server applications (like my case) and that the OAuth2 authentication is more made to authenticate a client.

Question

how to authenticate a server side application with an OAuth2 flow. or how to allow a server application to modify/manipulate playlists on youtube, spotify, deezer.

Details

i use node server.