System Administrator: Ability to Import Users via CSV / Excel File
While system administrator are limited to only have the following methods to create / import users:
* Local users: mattermost user create CLI, direct invite, team invite link
* External users: LDAP / AD / SAML
It will be good to have the ability to use CSV or Excel file to bulk import the users with specific formatting especially if the organization has a lot of customers and is not utilizing AD / LDAP / SSO.