Motivation for this change

Things done

Alternative idea to #119110

@Izorkin This probably won't make it - I just want to get some feedback regarding some problems with this approach and if that can be somehow improved. It would get a mess in the other PR.

@aanderse Pinging you is evil :D but it was your idea and I need some help. (Others are also welcome to help of course)

The important file is the module.

1. The problem is that some additional options for e.g. redis are needed that are not in the official peertube configuration (createLocally and passwordFile in this case). Should I use a) the current approach of splitting these up into two places, b) putting the options into settings where they are currently ignored by peertube, c) put all options that are usually needed outside of settings like before (inconsistent) or do you have another idea?
2. any idea how I can incoporate the settings.storage options without a lot of option declarations?
3. Is the way the passwords are read in now fine (the future encrypted nix secrets provisioning may unify this whole approach AFAICT)?
4. Anything else that comes to your mind in regard to the settings implementation?

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.