bug#45911: authorized-fields is not/badly documented

[raingloom]

On Sat, 23 Jan 2021 10:10:15 +0100
Ricardo Wurmus <rekado@elephly.net> wrote:

> raingloom <raingloom@riseup.net> writes:
> 
> > Okay, so I figured out that I should use a G-Expression if I want to
> > compute the file, instead of just include it. Still not sure how to
> > store it as Scheme data, but I have an untested idea involving the
> > "pipe" syntax for symbols.  
> 
> Use computed-file instead of local-file.
> 

I  know about computed-file, the issue is that the syntax of the key is
not strictly Scheme. The long hexadecimal block isn't parsed as a
number:
```
(with-input-from-file "/etc/guix/signing-key.pub" read)
...
/etc/guix/signing-key.pub:4:8: Unknown # object: #\C
```

Trying to store it as a module results in the same error.
So I can't just have an associative list of hostnames and signing keys
and filter it based on the hostname, I have to store each key as an
opaque file, completely bypassing the module system.