platform: add support for vultr

[bh7cw]

This adds fetching attributes and ssh keys from vultr, and tests via mockito.

Fixes #343

[lucab]

@bh7cw thanks for the PR! Did you manually check whether this produces the expected result on a real Vultr instance? If so, can you please paste as a comment here how does the final attributes-metadata content looks like?

[bh7cw]

@bh7cw thanks for the PR! Did you manually check whether this produces the expected result on a real Vultr instance? If so, can you please paste as a comment here how does the final attributes-metadata content looks like?

Test afterburn on vultr:

root@vultr:~/test# ./afterburn multi --provider vultr --attributes attr
Jul 13 18:08:22.652 INFO Fetching http://169.254.169.254/v1/hostname: Attempt #1
Jul 13 18:08:22.777 INFO Fetch successful
Jul 13 18:08:22.777 INFO Fetching http://169.254.169.254/v1/instanceid: Attempt #1
Jul 13 18:08:22.899 INFO Fetch successful
Jul 13 18:08:22.901 INFO Fetching http://169.254.169.254/v1/region/regioncode: Attempt #1
Jul 13 18:08:23.025 INFO Fetch successful

root@vultr:~/test# cat attr
AFTERBURNVULTRREGIONCODE=EWR
AFTERBURNVULTRHOSTNAME=vultr.guest
AFTERBURNVULTRINSTANCEID=39211897

root@vultr:~/test# curl http://169.254.169.254/v1/hostname
vultr.guest
root@vultr:~/test# curl http://169.254.169.254/v1/instanceid
39211897
root@vultr:~/test# curl http://169.254.169.254/v1/region/regioncode
EWR

root@vultr:~/test# **./afterburn multi --provider vultr --hostname hostname**
*Jul 13 18:09:45.675 INFO Fetching http://169.254.169.254/v1/hostname: Attempt #1
Jul 13 18:09:45.816 INFO Fetch successful*

root@vultr:~/test# cat hostname
vultr.guest


root@vultr:~/test# **./afterburn multi --provider vultr --ssh-keys root**
Jul 13 18:10:08.860 INFO Fetching http://169.254.169.254/v1/public-keys: Attempt #1
Jul 13 18:10:09.001 INFO Fetch successful*

[bh7cw]

Plus, private network, public network, ipv4, ipv6, and bgp are all optional for instances on vultr and user can chose to use or not.

[lucab]

Just a minor comment, code looks good otherwise. Thanks for manually testing too!

[lucab]

@bh7cw is this still WIP or ready for the final pass?

[bh7cw]

@lucab Thanks for review. This PR is ready for the final pass.

[lucab]

@bh7cw thanks for the patch, I did a manual test too and I didn't spot any issue. PR looks good to me, I've re-triggered the CI, will merge once green.