Feature: Unify the API for config vars

[a-alhusaini]

Original Message Deleted

It turned out that this feature was already implemented in Amber. But no one documented it.

You can override values defined inside .yml files in the config/settings.cr file. It essentially acheives the goals of this issue: Which is to provide a clean API for accessing configuration variables.

TODO: Document this feature.

[crimson-knight]

I like this.

Right now I can say that if there is an ENV declared that does exist in one of the environment yaml files, Amber will prefer the ENV declaration over the yaml file version.