feat(reva): Pass the multi-tenancy flag to reva services

This allows to pass the multi-tenant enablement flag as a shared config
option to the reva service. This needs to be done for all reva services
since it ends up in a global variable in reva that is only initialized
once, by the service that is the first to parse its config.
See https://github.com/opencloud-eu/opencloud/issues/1563 for details.

services/auth-basic/pkg/revaconfig/config.go

@@ -12,6 +12,7 @@ func AuthBasicConfigFromStruct(cfg *config.Config) map[string]interface{} {
 			"gatewaysvc":                cfg.Reva.Address,
 			"skip_user_groups_in_token": cfg.SkipUserGroupsInToken,
 			"grpc_client_options":       cfg.Reva.GetGRPCClientConfig(),
+			"multi_tenant_enabled":      cfg.Commons.MultiTenantEnabled,
 		},
 		"grpc": map[string]interface{}{
 			"network": cfg.GRPC.Protocol,