Create User manually without Mail-Server or Self-Registration

[lrsppp]

Is it possible to create a User manually without setting up a Mail Server or allowing registration? I would like to create around 20 accounts using predefined usernames and passwords (they should match the LDAP correspondents; which is only available in Enterprise Edition E10). Unfortunately, the Mail Server (managed by other party) I am using is not available at the moment. Therefore I cannot use the CLI to create user (mattermost user create ).

Does any workaround exist to write User Credentials into the postgresql database?