Fatal on ACME Client creation failure

- For production(*cough* Codeberg *cough*), it's important to not use
mock certs. So fail right from the start if this is the case and not try
to "handle it gracefully", as it would break production.
- Resolves #131

server/certificates/certificates.go

@@ -410,7 +410,7 @@ func SetupCertificates(mainDomainSuffix, dnsProvider string, acmeConfig *lego.Co
 
 	acmeClient, err = lego.NewClient(acmeConfig)
 	if err != nil {
-		log.Error().Err(err).Msg("Can't create ACME client, continuing with mock certs only")
+		log.Fatal().Err(err).Msg("Can't create ACME client, continuing with mock certs only")
 	} else {
 		err = acmeClient.Challenge.SetTLSALPN01Provider(AcmeTLSChallengeProvider{challengeCache})
 		if err != nil {