Rules to force www or no www.

www-enforcement

<IfModule mod_rewrite.c>
  RewriteEngine on
  
  # Set "protossl" to "s" if we were accessed via https://.
  RewriteRule ^ - [E=protossl]
  RewriteCond %{HTTPS} on
  RewriteRule ^ - [E=protossl:s]

  # To redirect all users to access the site WITH the 'www.' prefix,
  # (http://example.com/... will be redirected to http://www.example.com/...)

  RewriteCond %{HTTP_HOST} .
  RewriteCond %{HTTP_HOST} !^www\. [NC]
  RewriteRule ^ http%{ENV:protossl}://www.%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

  # To redirect all users to access the site WITHOUT the 'www.' prefix,
  # (http://www.example.com/... will be redirected to http://example.com/...)

  RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
  RewriteRule ^ http%{ENV:protossl}://%1%{REQUEST_URI} [L,R=301]
  
</IfModule>