The goal of the vars proposal is to have a generic backend-agnostic solution for secret deployment and generation (example usecases include the user password, host ssh keys, etc).
Existing work includes:
- Clan’s vars (the idea stemmed from here)
- Agenix rekey (agenix specific implementation)
- The old nixpkgs vars PR (the first proposal of adding this to NixOS)
- Vars-ng (the most recent manifestation of the proposal AFAIK?)
- The various frameworks for secret deployment (but not generation): agenix, sops-nix, etc
- The various proposals for the contract API (way more general than vars)