WIP: nixos/frr: refactor, test bgp

[mweinelt]

Description of changes

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
• For non-Linux: Is sandbox = true set in nix.conf? (See Nix manual)
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 22.11 Release Notes (or backporting 22.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
  • (Release notes changes) Ran nixos/doc/manual/md-to-db.sh to update generated release notes
• Fits CONTRIBUTING.md.

[mweinelt]

@woffs Are you possibly interested in finishing this up? It would be nice to have this as both validation and example.

[thillux]

@mweinelt I'd like to work on this, if I find some time. Ok for you, if I "steal" here and open another PR?

My testing interest is bgp, ospf and bfd.

[woffs]

@woffs Are you possibly interested in finishing this up? It would be nice to have this as both validation and example.

sorry for not replying, I did not have the time yet, so it's great if @thillux wants to take it away!