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

use the new one we're setting up on a new filesystem

Update nixpkgs.

See merge request !223

Monitoring/tahoe metrics collector: Add systemd dependency declarations

See merge request !220

Thanks go out to @tomprince!

Weekly nixpkgs update.

See merge request !221

Update nixpkgs.

See merge request !219

Tryfix the starting of the timer before tahoe is updated.

Update to version of ZKAPAuthorizer that includes a Tahoe with openmetrics support.

Closes #90

See merge request !218

Add dashboard for tahoe-lafs

Closes privatestorageops#396

See merge request !217

This adds a detailed dashboard for tahoe-lafs running on one node.

Monitoring: Add regular scraping for Tahoe OpenMetrics statistics

Closes privatestorageops#285

See merge request !216