UI: handle reused MD RAIDs that are already included in the configuration

[ancorgs]

Problem

If a storage configuration includes reusing an existing MD RAID device, such a device is not displayed at the Agama configuration UI. But actually that case is not so different from using a disk.

Solution

This extends the component ConfigEditor to also display reused MD RAIDs, offering the same capabilities that are there for disks (like creating partitions or defining what to do with the existing ones).

This does not offer any possibility to remove the RAID from the configuration or to add a new RAID. It only works with RAIDs that are already present at the loaded configuration.

Implementation notes

Some of the pre-existing components like DriveEditor, SpacePolicySelection or PartitionsPage use the old queries at config-model.ts to communicate with the backend. Something that is deprecated in favor of https://gist.github.com/joseivanlopez/a8d1e4269e6f1c8d41837dfd89fb556d?permalink_comment_id=5569616

This pull request gives several steps on the agreed direction, but a few inner components still use the old approach.

Testing

• Tested manually
• Backend tests reorganized and expanded
• Frontend tests updated

[coveralls]

coverage: 62.794% (-0.2%) from 63.008%
when pulling 8e6e5ce on ancorgs:raid_editor
into 9116f0e on agama-project:master.

[joseivanlopez]

As discussed in a meeting, we will adapt the storage editor components (e.g., DriveEditor) to receive a list and an index instead of a device object. This will allow to:

• Simplify the model types (list and listIndex properties are not needed).
• All the components work in a similar way (DriveEditor, PartitionPage, etc). They receive a list and an index and each component retrieves the device from the model if needed.
• The components always have the needed info for generating an url.
• The partitions and logical volumes can also be referenced by an index, so it opens the door to have partitions and lvs without a mount path.

These changes will be done once we need to allow creating partitions without a mount path (e.g., for manually creating physical volumes).

[joseivanlopez]

LGTM