Fatal on ACME Client creation failure (#133)

- 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

CC @6543

Co-authored-by: Gusted <williamzijl7@hotmail.com>
Reviewed-on: https://codeberg.org/Codeberg/pages-server/pulls/133
Reviewed-by: 6543 <6543@obermui.de>
Co-authored-by: Gusted <gusted@noreply.codeberg.org>
Co-committed-by: Gusted <gusted@noreply.codeberg.org>

server/certificates/certificates.go

@@ -414,7 +414,7 @@ func SetupCertificates(mainDomainSuffix []byte, dnsProvider string, acmeConfig *
 
 	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 {