hcloud context: add JSON output

[martinvonwittich]

TL;DR

I want to iterate over all contexts I have set up in hcloud. Unfortunately hcloud context list does not support JSON output:

server ~ # hcloud context list -o json
hcloud: invalid output option: json

So in the past I improvised by parsing the normal output:

server ~ # hcloud context list --output noheader -o columns=name | head -n1
Hosting             

This worked fine in hcloud 1.43:

server ~ # hcloud-1.43.1 context list --output noheader -o columns=name | head -n1 | cat -A
Hosting$

But with hcloud 1.61 the output is now padded with spaces, which broke my parsing:

server ~ # hcloud-1.61.0 context list --output noheader -o columns=name | head -n1 | cat -A 
Hosting             $

I think JSON output would be the sensible solution here.

Expected behavior

I want cleanly parseable output that doesn't break when the human-readable output format is changed.