Technical Story: refactor the way configuration variables are set prior to deploying

[AlexisVLRT]

Definition of ready Ready

Description We have vars, vars_base, and vars_additionnal that are treated as sh scripts. This is not clear and well designed.

Refactor this to have a json file and a parser

Definition of done

• Behavior is unchanged from the user's perspective
• One single json file contains all the variables
• A parser to export the variables from the json file so they are accessible by Terraform through env-vars
• We don't want to just create a Terraform variables file because some variables depend on each others, and we want to avoid having a monolithic sh script that does it all at once

[AlexisVLRT]

Done