Migrates to Maven Central for package publishing

This release does not bring any meaningful changes to the libray code itself. The purpose is to modify the gradle build setup and the accompanying github workflows to switch publishing away from github packages and into maven central.
An additional goal was to use a GPG key in order to sign packages.

Fixes hanging slack hook

Minor fix - slack hook would sometimes hang when multiple messages (>2) where sent within the space of a few seconds.
Fixed by switching to the CloseableHttpClient and closing the response after sending.

Get Log Level

Adds the getLogLevel method to the Log Level Service that allows the client to check on the logger level at runtime.

Log Level Service

This release adds a service wrapper around logback for changing log levels at runtime.
As a side note the configuration class was refactored to a more functional approach.

List support

Adds support for retrieving comma-separated lists of strings, integers, doubles or booleans

Initial

Library for environment configuration and slack hooks