centrifugo: add release note and assertion for compatibility

- `pkgs.nextcloud28` has been removed since it's out of support upstream.

- `centrifugo` was updated to v6, which uses a new config format. See [upstream documentation](https://centrifugal.dev/docs/getting-started/migration_v6) for migration.

- `teleport` has been upgraded from major version 16 to major version 17.

  Refer to [upstream upgrade instructions](https://goteleport.com/docs/upgrading/overview/)

  and [release notes for v17](https://goteleport.com/docs/changelog/#1701-11152024).

  };

  config = lib.mkIf cfg.enable {

    assertions = [

      {

        assertion =

          (lib.versionAtLeast cfg.package.version "6") -> (!(cfg.settings ? name) && !(cfg.settings ? port));

        message = "`services.centrifugo.settings` is v5 config, must be compatible with centrifugo v6 config format";

      }

    ];

    systemd.services.centrifugo = {

      description = "Centrifugo messaging server";

      wantedBy = [ "multi-user.target" ];