HAProxy mappings

[papdee]

Need help mapping below into HAProxy backend:

acl existing-x-forwarded-host req.hdr(X-Forwarded-Host) -m found
http-request add-header X-Forwarded-Host %[req.hdr(Host)]/documentserver-virtual-path unless existing-x-forwarded-host
reqrep ^([^\ :])\ /documentserver-virtual-path/(.) \1\ /\2
server onlyoffice-documentserver backendserver-address:80