Редирект с https на http при отсутствии сертификата
RewriteCond %{SERVER_PORT} =^443$ [OR]
RewriteCond %{HTTP:X-Forwarded-Proto} https
RewriteRule ^(.*)$ http://%{SERVER_NAME}%{REQUEST_URI} [R=301,L]
RewriteCond %{HTTP:X-Forwarded-Proto} https RewriteCond %{REQUEST_URI} (.*)\.txt$
RewriteRule ^robots\.txt robots-https.txt [L]