Btrfs snapshot support

[jelly]

Show snapshots of a subvolume in the detail view.

[jelly]

@mvollmer I thought a bit on how we could implement filtering:

We could come up with a system where we don't have to hardcode the "filters" in but we could register filters for pages which want that.

register_filter(display_name, property_name)

This registers a filter which lives in pages.jsx, then we use these filter with property_name and filter_properties.

Alternatively, we just hardcode filters:

PAGE_FILTER_SNAPSHOT = 'snapshot'

Page/Card can have filter_properties which contains the key we are interested for with the value. State can come later.

I'm not thinking of introducing something like a filter component. But maybe it is interesting to have something usable.

[mvollmer]

@mvollmer I thought a bit on how we could implement filtering:

I think this is a bit too much machinery. Let's just do what we need, and nothing more.

[jelly]

Alright, after the discussion today in standup:

• First pass, show snapshots under a subvolume
• Second pass, hide snapshots

[jelly]

@garrett question from @mvollmer did we decide on the design yet?

So my idea is:

• Hide snapshots on the overview
• List snapshots of a subvolume in the subvolume detail page.

[garrett]

@jelly: Yes, I think that's what we want. Good, simple summary.

I think we (you and/or @mvollmer and I) agreed on that a while ago somewhere? Perhaps in a video call? Perhaps in an issue? I don't remember where, but if we all agree on that, then that's great.

To restart: I definitely do not want them on the overview (and never have) and I think the details pages are the right places for the snapshots.