### Description
When I rewrite from native to Lua syntax, I find that `pv_www_authenticate` has no corresponding implementation, can we add it?
### Expected behavior
#### Actual observed behavior
#### Debugging Data
``` (paste your debugging data here) ```
#### Log Messages
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``` (paste your log messages here) ```
#### SIP Traffic
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``` (paste your sip traffic here) ```
### Possible Solutions
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### Additional Information
* **Kamailio Version** - output of `kamailio -v`
``` (paste your output here) ```
* **Operating System**:
<!-- Details about the operating system, the type: Linux (e.g.,: Debian 8.4, Ubuntu 16.04, CentOS 7.1, ...), MacOS, xBSD, Solaris, ...; Kernel details (output of `uname -a`) -->
``` Kamailio 5.8.2 Lua 5.1.4 ```