add systemd to letsencrypt installer (#8289)

* add systemd to letsencrypt

* Better readability of systemd change

Co-authored-by: Sebastian Feustel <sebastian.feustel@aei.mpg.de>

resources/install-letsencrypt-cert.sh

     CERT_CRT_ESC=$(echo $CERT_CRT_ESC | sed 's/\//\\\//g')
     sed -i "s/ssl_certificate\ \/etc\/jitsi\/meet\/.*crt/ssl_certificate\ $CERT_CRT_ESC/g" \
         $CONF_FILE
-
-    echo "service nginx reload" >> $CRON_FILE
-    service nginx reload
+    
+    if type service >/dev/null 2>&1
+    then 
+        service nginx reload
+        echo "service nginx reload" >> $CRON_FILE
+    else 
+        systemctl reload nginx.service 
+        echo "systemctl reload nginx.service" >> $CRON_FILE
+    fi
+    
 elif [ -f /etc/apache2/sites-enabled/$DOMAIN.conf ] ; then
 
     /usr/bin/certbot certonly --noninteractive \
     CERT_CRT_ESC=$(echo $CERT_CRT_ESC | sed 's/\//\\\//g')
     sed -i "s/SSLCertificateFile\ \/etc\/jitsi\/meet\/.*crt/SSLCertificateFile\ $CERT_CRT_ESC/g" \
         $CONF_FILE
-
-    echo "service apache2 reload" >> $CRON_FILE
-    service apache2 reload
+    
+    if type service >/dev/null 2>&1
+    then 
+        service apache2 reload
+        echo "service apache2 reload" >> $CRON_FILE
+    else 
+        systemctl reload apache2.service 
+        echo "systemctl reload apache2.service" >> $CRON_FILE
+    fi
 fi
 
 # the cron file that will renew certificates