Revert backwards incompatible reva config changes

The commit of unifying the Reva Client config introduced some backwards
incompatible changes to the config structures and yaml config tags. For
the "thumbnails", "webdav" and "notifications" service. This reverts the
changes on the service and introduces TLS options in a backwards
compatible manner.

services/notifications/pkg/channels/channels.go

@@ -27,7 +27,15 @@ type Channel interface {
 
 // NewMailChannel instantiates a new mail communication channel.
 func NewMailChannel(cfg config.Config, logger log.Logger) (Channel, error) {
-	gc, err := pool.GetGatewayServiceClient(cfg.Notifications.Reva.Address, cfg.Notifications.Reva.GetRevaOptions()...)
+	tm, err := pool.StringToTLSMode(cfg.Notifications.RevaGatewayTLSMode)
+	if err != nil {
+		logger.Error().Err(err).Msg("could not get gateway client tls mode")
+		return nil, err
+	}
+	gc, err := pool.GetGatewayServiceClient(cfg.Notifications.RevaGateway,
+		pool.WithTLSCACert(cfg.Notifications.RevaGatewayTLSCACert),
+		pool.WithTLSMode(tm),
+	)
 	if err != nil {
 		logger.Error().Err(err).Msg("could not get gateway client")
 		return nil, err