We have tried to use command such as
find / -type f -exec grep -H 'text-to-find-here' {} \;
But no files with full sting "Please provide user name and password to authenticate" were found. I suppose link to the text string should be somewhere into the file General.php.
Also we have found in to the PortalCustomization.php following strings
$this->portalTitle = rpc_get_string(rpc_get_sub($response, "m_title"));
$logger->debug (sprintf ("Title: %s", $this->portalTitle));
But I am not sure, can we just replace rpc_get_string(rpc_get_sub($response, "m_title")) with required text.
And also we have same issue with pages with OTP SMS and user password change.