Update nixos to 21.11

See merge request !222

This also update ZKAPAuthorizer to a python3 using version.

This is disallowed in nixos 21.11 as it is a potential security issue.

Update nixpkgs.

See merge request !238

Collect some monitoring host details automatically.

See merge request !234

update to the new host key

See merge request !235

Fix megacli2prom out-of-range error

See merge request !229

bump to the ZKAPAuthorizer branch that pulls in and is compat w/ the new Tahoe-LAFS

Closes #98

See merge request !230

Update nixpkgs.

See merge request !231

Merge most of the code from the `customize-*.nix` nodes into the base modules.

See merge request !233

move all of the hosts from 192.168.67.x to 192.168.56.x

Closes #101

See merge request !232

The VirtualBox documentation says this is the network to use for host-only
networking.

Take what I learned from @tomprince in
https://whetstone.privatestorage.io/privatestorage/PrivateStorageio/-/merge_requests/220#note_17605 :
Assigning a service a `startAt' will make timer.target start it,
no need to also have it `wantedBy' multiuser.target.

Also add megacli2prom to the path even if it should be already because
of megacli2prom.  Better be safe than sorry.

use a different state directory for the issuer's voucher database

Closes privatestorageops#399

See merge request !226

mkfs silently truncates "zkapissuer-database" to "zkapissuer-datab" and
everything falls apart.

and the update takes care of starting it automatically

The point is this is where PaymentServer's persistent state goes.  That
includes vouchers but might include more stuff too.

The hardware modules can now configure this fileSystem in a way appropriate
for themselves and the issuer module can enable that configuration when it is
enabled itself.

now all nodes load the issuer module so we can always supply issuer
configuration, where it makes sense to do so, even on systems where the issuer
is not going to be enabled.

if that sounds silly read the comment in default.nix

Update nixpkgs.

See merge request !227

bump ZKAPAuthorizer to the fixed version

Closes bizops#220

See merge request !225