### 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 ```