Add support for product modes

[imobachgs]

PED-14307

This PR introduces the concept of product modes.

Use case

From now on, if you select SLES 16.1, you can choose between installing the system following the traditional partitioning approach (with a read/write root like 16.0) or using the transactional mode.

Modes

Modes support is not limited to the described use case. Each mode can redefine the software or the storage sections of the product. In the previous case:

• It selects the transactional_base or enhanced_base depending on the mode.
• Defines a different partitioning layout.

Defining modes

The modes definition lives under the modes key. It includes:

• Some meta-data (id, name, and description).
• Optionally, a software key, which is merged with the base one.
• Optionally, a storage key which is merged with the base one.

modes:
  - id: standard
    name: Standard
    description: Standard system

    software:
      mandatory_patterns:
        - enhanced_base

  - id: immutable
    name: Immutable
    description: Immutable system with atomic updates

    software:
      mandatory_patterns:
        - transactional_base

Testing

• Added a new unit test
• Tested manually (in progress)

Screenshots

[joseivanlopez]

I am not sure about this. For now, I would assume the storage section is totally overried by the mode.

[jreidinger]

well, similar is for software...but in current usage in products it is more like product nothing and modes everything for both.

[imobachgs]

I did in this way just for consistency with software. For instance, you might want to have a common list of user patterns and add only the differences, instead of repeating the whole list.

If you want the whole list to be replaced, well, you just specify an empty list in the base configuration.

[joseivanlopez]

LGTM