Add an option to disable user registration

[mxmv]

When a limited number of people are involved in editing of a public wiki, it is useful to prevent registration of new users.

[scragg0x]

Added in: b8531a0347ad6a4ab12862d835ddba9818904c28

This will create a user from the command line and print a random password. realms-wiki auth create_user foo foo@gmail.com

You can also set a password with --password. realms-wiki auth create_user foo foo@gmail.com --password bar

Create a config.json in the root directory and add this to disable registration:

{
  "REGISTRATION_ENABLED": false
}

[lanrat]

Looks like the syntax changed a but, the new syntax is: realms-wiki cli create_user foo foo@gmail.com --password bar