User management: Option to bulk create users & add users manually

As each user needs to exist in Razuna before you can add them to your workspaces and teams, this option would alleviate the pain point of having users register first.

The import should have the following options:

• email address
• name
• team(s)
• password (or leave emtpy to create one)
• send an email to all users after import
• workspace(s)

Apart from the import, we should also have an option to create a user manually.