- Also alert on "negative" (== receiving) errors
- Use 'rate' so we can get out of the reporting if situation normalizes

Grafana 8 recommends these for added performance and capabilities.

- (tryfix) Switch to Loki datasource;
- Filter requests to metrics instead of all GET;
- Show the last week by default
- Show log times

Interesting and not quickly fixable as it looks like: the
GET ... line comes *after*  the result.  We might be logging
this wrong to begin with, but probably this is some next
gen AI line ordering intelligence

Or rather, let it listen only on localhost.
I thought Grafana needed it, or Promtail needed it, but I don't remember
clearly, the web doesn't say clearly, and on my local dev stack
Promtail/Loki seems to still work just fine without GRPC on the network.

OMG look at teh genius of it

Do some name resolution for those poor computers

Improve factoring by removing those `/etc/hosts` entries

And avoid the infinite loop @tomprince was encountering in !258

rename sshPrivateKeyFile also in other files

Besides migrating all charts to the faster and more capable Grafana 8
TimeSeries charting tool this mainly introduces two panels to view
the logs of PaymentServer.  It has some naive and minimal filtering
in place to only show lines that are not caused by the metrics gathering
itself or that I just deemed to be OK (like "GET" requests) so we
hopefully catch those dreaded "Unexpected Exception" lines.

Fixes privatestorageops#207.

Should be pure refactoring

This is my latest version of this, updated to work with the
packages in NixOS 21.05.

Note that changing the origin repository in the on-node deployment checkout
is also required.

See https://whetstone.private.storage/privatestorage/privatestorageops/-/merge_requests/197#note_19071

Older versions of nixpkgs allowed you to specify multiple keys by having
newline separated keys in your string. However, this worked essentially by
accident, and is now explictly disallowed.

I noticed this because I had configured multiple keys for the local grid.  This
isn't currently impacting my ability to work, but it seems like a worthwhile
improvement anyway. This will be necessary (for example) if/when multiple people are
given root access to our storage nodes.

Source: https://whetstone.privatestorage.io/privatestorage/PrivateStorageio/-/merge_requests/237#note_18712

Thanks to @jcalderone for the suggestion!

The current code evaluates our custom packages once for each node, which adds
signifcant amount of time to evaluate a grid. We can reduce this, by adding the
custom package set as an attribute to the nixpkgs set we pass to morph.

This doesn't change how we refer to those packages, as we continue to expose the
custom package set as a module attribute.

These are the times to evaluate all three grids (on a partially loaded system),
when there was nothing new to build:

```
before:
real	2m27.837s
user	3m35.528s
sys	0m3.722s

after:
real	1m12.748s
user	1m34.047s
sys	0m3.346s
```

Fixes privatestorageops#408

This also update ZKAPAuthorizer to a python3 using version.

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

Also strip that domain component from the labels collected.

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.

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