ensure lowercase backend in the command

accounts/pkg/command/server.go

@@ -30,6 +30,8 @@ func Server(cfg *config.Config) *cli.Command {
 				cfg.HTTP.Root = strings.TrimSuffix(cfg.HTTP.Root, "/")
 			}
 
+			cfg.Repo.Backend = strings.ToLower(cfg.Repo.Backend)
+
 			// When running on single binary mode the before hook from the root command won't get called. We manually
 			// call this before hook from ocis command, so the configuration can be loaded.
 			if !cfg.Supervised {