[bug#26685] certbot service experience

[Christopher Allan Webber <cwebber@dustycloud.org>]

Ludovic Courtès writes:

> Hello!
>
> Since everyone was so hesitant I was so blissful ;-), I went ahead and
> pushed this patch as commit c2e5d74997bdb57dc35e0189188c6917cd5f0f19!
> \o/
>
> I think it’s better than the status quo, because even if it’s not
> perfect, it *is* useful as it is.  We can start from here if there are
> ideas on how to improve it.
>
> Ludo’.

Yay!  But oh nooooo!  I really should have replied to this!  I had
stopped working on it because I got overloaded with final-push situation
in ActivityPub.

Maybe this is worth moving to the mailing list instead, but one reason I
didn't push it was I had discovered a significant and serious
issue... building a system based off of its config is no longer
determistic based off of the system config alone... because this
checks for the rpesence of nginx-server-configuration-ssl-certificate
at *build* time of the system config.  The following code is the
culprit:

  (define (emit-nginx-server-config server)
    ;; [...]
      (for-each
       (match-lambda
        ((record-key . file)
         (if (and file (not (file-exists? file)))
             (error
              (simple-format
               #f
               "~A in the nginx configuration for the server with name \"~A\" does not exist" record-key server-name)))))
       `(("ssl-certificate"     . ,ssl-certificate)
         ("ssl-certificate-key" . ,ssl-certificate-key)))

Relatedly, the current setup has these defaults:

  (ssl-certificate     nginx-server-configuration-ssl-certificate
                       (default "/etc/nginx/cert.pem"))
  (ssl-certificate-key nginx-server-configuration-ssl-certificate-key
                       (default "/etc/nginx/key.pem"))

IMO they should probably default to #f so that looking for the files
doesn't fail to boot nginx.