MAS CLI installation needs case validation for language selection

[BrendanFishback]

Feature and motivation

During the MAS / Manage installation process using the CLI, one of the steps is to provide secondary / additional languages. If you provide an additional language in a lower case (for example, 'fr' instead of 'FR') it will continue without returning a warning/error message. However, the installation will still fail later due to the lowercase language code.

The suggestion is for the CLI to either immediately prompt an error if a lowercase language code is provided, or have the installer automatically convert the lowercase language code into its proper capitalized form.

Usage example

This enhancement would avoid a lot of situations where time is lost due to failed installations because the error would be caught much earlier.

[durera]

We can easily convert the input to lowercase automatically