testing/lua-resty-postgres: new aport

https://github.com/azurewang/lua-resty-postgres Nonblocking Lua PostgreSQL driver library

This is a very useful library for OpenResty applications, and we don't currently have any other library in Alpine which can used to access Postgres from OpenResty. I am personally using it in production. Unfortunately, the original author has not accepted any patches (or responded to messages from users) for a few years, so I wonder if it may eventually become necessary to fork it.

I've added support for PG's "trust" authentication mode and might add support for other authentication modes, or other features of PG, as I personally need them. If anyone else starts using this PG package and requests support for more PG features, I am also potentially available to implement support.