subcommands:
update-users (u) [USER]... update user authorized_keys files
- add-id-certifier (c+) KEYID import and tsign a certification key
+
+ add-id-certifier (c+) [KEYID|FILE] import and tsign a certification key
--domain (-n) DOMAIN limit ID certifications to DOMAIN
--trust (-t) TRUST trust level of certifier (full)
--depth (-d) DEPTH trust depth for certifier (1)