Create plan for a major refactoring of configuration parsing

Context

Related to this thread. See it for additional context.

Task

Investigate and define a feasible path to replace our custom configuration parser with available open source libraries, ideally using struct tag annotations. Examples: github.com/kelseyhightower/envconfig and github.com/knadh/koanf.

The goal is to:

• Discard the custom implementation at parser.go;
• Cleanup parsing logic that spread over to configuration.go;
• Annotate the config struct with not just the yaml parser tags but also with env var tags (where the latter override the former if set).