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/config/defaults/defaultconfig.go

@@ -88,6 +88,10 @@ func EnsureDefaults(cfg *config.Config) {
 			cfg.GRPC.TLS.Key = cfg.Commons.GRPCServiceTLS.Key
 		}
 	}
+
+	if cfg.Commons != nil {
+		cfg.HTTP.TLS = cfg.Commons.HTTPServiceTLS
+	}
 }
 
 func Sanitize(cfg *config.Config) {

services/thumbnails/pkg/config/http.go

@@ -1,8 +1,11 @@
 package config
 
+import "github.com/owncloud/ocis/v2/ocis-pkg/shared"
+
 // HTTP defines the available http configuration.
 type HTTP struct {
-	Addr      string `yaml:"addr" env:"THUMBNAILS_HTTP_ADDR" desc:"The bind address of the HTTP service."`
-	Root      string `yaml:"root" env:"THUMBNAILS_HTTP_ROOT" desc:"Subdirectory that serves as the root for this HTTP service."`
-	Namespace string `yaml:"-"`
+	Addr      string                `yaml:"addr" env:"THUMBNAILS_HTTP_ADDR" desc:"The bind address of the HTTP service."`
+	TLS       shared.HTTPServiceTLS `yaml:"tls"`
+	Root      string                `yaml:"root" env:"THUMBNAILS_HTTP_ROOT" desc:"Subdirectory that serves as the root for this HTTP service."`
+	Namespace string                `yaml:"-"`
 }