Redirect to preferred domain, force SSL, and require HTTP Auth

.htaccess

# Redirect domain and force SSL #
RewriteEngine On
RewriteCond %{HTTP_HOST} !^example.com$ [OR,NC]
RewriteCond %{SERVER_PORT} 80
RewriteRule ^(.*)$ https://example.com/$1 [R=301,L]

<If "%{HTTPS} == 'on'">
  # Password Protect Directory #
  AuthUserFile /srv/www/example.com/.htpasswd
  AuthName "Enter username and password"
  AuthType Basic
  Require valid-user
</If>