To Debug ngx_http_auth_ldap_module

I get the error message `[error] 21#21: *3 http_auth_ldap: ldap_search_ext() failed (-7: Bad search filter)`, and would like to debug why it ended up with bad search filter.

From the module, I can see debugs which may be helpful in my investigation
https://github.com/kvspb/nginx-auth-ldap/blob/master/ngx_http_auth_ldap_module.c

in `/etc/nginx/nginx.conf`
I have tried these two options, but still does not print the debug to the output console

```
error_log /var/log/nginx/error.log debug;
error_log /var/log/nginx/error.log debug_http;
```

Have anyone successfully turn on debug for ngx_http_auth_ldap_module ?

Start with ngx_http_auth_ldap_module.c and the nginx.conf error_log directives, then reproduce the reported ldap_search_ext() bad-search-filter error. Done means identifying why the module's debug output is not appearing and documenting a working way to enable or inspect it.

Written by the indexing model from the issue text.