Refactor Config class

[arasHi87]

The original design for setting environment variables was to leave env empty and let the Config defaults populate, but GitHub Action automatically parses env-sample and applies it to the environment variables as str, which breaks the flow and we don't get the expected variables and types.

So this question focuses on how to refactor the Config class, and the following functionality is what we expect the Config class to have.

• We can assign the type of variable we want, and automatically validate it
• Filter None and blank