Hosting.de: Allow using as registrar only (#1307)

Previously, the provider would always try to fetch the zone config for
the domain. But that doesn't work if the domain's DNS is not managed
through Hosting.de.

With this patch, getDomainConfig() instead filters directly on the
domain name instead of re-fetching it from the zone.

Co-authored-by: Tom Limoncelli <tlimoncelli@stackoverflow.com>

providers/hostingde/api.go

@@ -20,15 +20,10 @@ type hostingdeProvider struct {
 }
 
 func (hp *hostingdeProvider) getDomainConfig(domain string) (*domainConfig, error) {
-	zc, err := hp.getZoneConfig(domain)
-	if err != nil {
-		return nil, fmt.Errorf("error getting zone config: %w", err)
-	}
-
 	params := request{
 		Filter: filter{
 			Field: "domainName",
-			Value: zc.Name,
+			Value: domain,
 		},
 	}