Introduce TLS Settings for go-micro based http services

TLS for the services can be configure by setting the "OCIS_HTTP_TLS_ENABLED",
"OCIS_HTTP_TLS_CERTIFICATE" and "OCIS_HTTP_TLS_KEY" environment variables.
Currently the ocis proxy is this only service that directly accesses backend
services. It determines whether to use TLS or not by looking a the new registry
metadata "use_tls". As specific CA Cert for certificate verification
can be set with the "PROXY_HTTPS_CACERT" environment variable.

services/thumbnails/pkg/server/http/server.go

@@ -1,6 +1,8 @@
 package http
 
 import (
+	"fmt"
+
 	"github.com/go-chi/chi/v5/middleware"
 	ocismiddleware "github.com/owncloud/ocis/v2/ocis-pkg/middleware"
 	"github.com/owncloud/ocis/v2/ocis-pkg/service/http"
@@ -14,7 +16,8 @@ import (
 func Server(opts ...Option) (http.Service, error) {
 	options := newOptions(opts...)
 
-	service := http.NewService(
+	service, err := http.NewService(
+		http.TLSConfig(options.Config.HTTP.TLS),
 		http.Logger(options.Logger),
 		http.Name(options.Config.Service.Name),
 		http.Version(version.GetString()),
@@ -22,6 +25,12 @@ func Server(opts ...Option) (http.Service, error) {
 		http.Address(options.Config.HTTP.Addr),
 		http.Context(options.Context),
 	)
+	if err != nil {
+		options.Logger.Error().
+			Err(err).
+			Msg("Error initializing http service")
+		return http.Service{}, fmt.Errorf("could not initialize http service: %w", err)
+	}
 
 	handle := svc.NewService(
 		svc.Logger(options.Logger),