This is split off from SAT-40213 because that is a large issue.

Goal

Create the initial migration subcommand with the basic structure, based on the PoC from SAT-38734.

It should be able to read and parse answer files. Parsed answer files are mapped, but not all answers have to have a map yet. Implicitly this means you should be able to test it with an empty answer file, containing only an empty hash.

Acceptance criteria

• The user can run the migration subcommand
• The subcommand accepts a parameter for the answer file location
• When no answer file location is provided, it attempts to read it from foreman-installer's current answer file
• When no answer file can be determined, an error is shown
• The answer file is read and parsed
• Any entries it can map are stored to the answers
• An error is shown when it finds unmappable answers

Open questions

• What should the command be called
• Does it need its own subcommands for the various stages (import, analyze, etc)
• Does it need a noop function?