We need a "reverse login model" instead of a "through-thread" I dont want to login to Site A with my Site B creds. I needa locally controlled app that ASKs me

We need a "reverse login model" instead of a "through-thread" I dont want to login to Site A with my Site B creds. I needa locally controlled app that ASKs me for a token to be even allowed access to my data, and that system, should I choose to delete an account, will delete my data from said site. We passed an act with that intent "data portability"