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/graph/pkg/server/http/server.go

@@ -3,6 +3,7 @@ package http
 import (
 	"crypto/tls"
 	"crypto/x509"
+	"fmt"
 	"os"
 
 	"github.com/cs3org/reva/v2/pkg/events/server"
@@ -24,7 +25,8 @@ 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.Namespace(options.Config.HTTP.Namespace),
 		http.Name("graph"),
@@ -33,6 +35,12 @@ func Server(opts ...Option) (http.Service, error) {
 		http.Context(options.Context),
 		http.Flags(options.Flags...),
 	)
+	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)
+	}
 
 	var publisher events.Stream