Expose configuration keys as static variables in swift

[DanielSumara]

variants generate Variants structure for iOS project. This struct contains encrypted env variables which we can access in safe manner using eg. print(Variants. Secrets.propertyName). ENVIRONMENT VARIABLES

It would be great improvement if we could access in the same manner other defined properties instead using string as keys.

We can replace print(Variants.configuration["A_PROPERTY"]) using (Variants.configuration[.aProperty])

[gderaco]

Be sure to keep the old way to guarantee retrocompatibility