Nothing is stored on my side except a list of Spotify ID's for the future one-time payment and a counter for the amount of playlists created by each. that's all. Because I am using a third-party tool for download statistics and origin (AppsFlyer) I added this clause but I am really not collecting any data.

I am not the actual developer. I thought of the idea and researched the Spotify API. I hired developers for the actual job.