[Service] Alternative location for volumes

[ancorgs]

Problem

The storage proposal allows to specify what to do in order to allocate any volume:

• Use the default location (new partition or new LV)
• Create it in a given disk as a new partition
• Create it as a new LV in a new dedicated VG on top of a given disk
• Reformat an existing device
• Mount an existing device

Everything is possible, no matter whether the default target is a disk or a new LVM VG.

So far, it was not possible to use the Agama D-Bus settings to specify that to the proposal, so all volumes always used the default location.

Solution

This adds two new attributes to the D-Bus definition of a volume: Target and TargetDevice.

Internally, this is represented by a new class VolumeLocation with two attributes:

• target: which specifies how to allocate the volume
• device: the name of the target device, the exact meaning depends on target

The new class and the possible targets follow the same approach of SpaceSettings and its policies.

Testing

• Added several unit tests
• Tested manually by hacking the web UI a bit (see screenshots below)

Screenshots

Hacking the web UI to set Target to filesystem and TargetDevice to /dev/vdb5 (which contains a Btrfs file system).

Hacking the web UI to set Target to new_vg and TargetDevice to /dev/vdc.

[coveralls]

coverage: 74.41% (+0.06%) from 74.346%
when pulling 5270b4b on volume_location
into 2c81aca on master.

[joseivanlopez]

Looks good, but I miss a changelog entry. The only bad thing is that I will eat a lot of conflicts with #1068.

[joseivanlopez]

I think it needs brackets, see {.targets}

[joseivanlopez]

The equivalent for the default device are called Target and Device. I am not sure if we should follow the same naming or not.

[ancorgs]

I like the current names because it shows the relationship between both fields. I mean, TargetDevice is actually some kind of "details" field for the Target one.

[joseivanlopez]

Ok, makes sense. Then, I will adapt my PR to follow the same approach.

[joseivanlopez]

LGTM