providers/hetzner: add support for Hetzner Cloud

[mhutter]

• Add Hetzner Cloud as a provider
• Userdata endpoint is http://169.254.169.254/hetzner/v1/userdata

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Figured out this is actually trivial, so here's a PR.

Supersedes #667 and #1262 which I cannot push commits to.

Relates: coreos/fedora-coreos-tracker#1324

[apricote]

Hetzner Cloud employee here 👋 Looks good from a metadata service perspective.

We do have a go metadata client, but I think that's overblown for this specific use case. (And I just noticed that its missing the userdata endpoint anyway)

Some notes about general support for Ignition metadata in Hetzner Cloud:

• The hcloud CLI has some cloud-init specific helper utility when users pass in multiple files using the hcloud server create --user-data-from-file flag. I do not think that specifying multiple files makes sense in Ignition (they would need to be merged somehow)
• The "Create Server" page in the web console has some cloud-init specific help text for the User Data input

[mhutter]

Yes, I noticed the cloud-init specifics as well. From a technical standpoint, I did some testing where I "chain-load" the Ignition config from your userdata service, and it works as expected. (see https://github.com/mhutter/hcloud-packer-coreos/blob/7c11c5a774c05ba3b4df388e4cc1a82d8a2a5d05/files/chain.bu)

The rest I just ignored :D

[travier]

@apricote Thanks for the review!

[prestist]

@mhunter Thank you so much for putting in the time and effort on adding hetzner.

After looking over this everything looks great, I just have a small nit on the commit

I would prefer it to be "providers/hetzner: add support for Hetzner Cloud" there are no guidelines for this, but I know in this repo we tend to have our commits be in the form of "providers/xyz: work that was done"

[mhutter]

@prestist Ah, I see! I only looked at the last couple of commits, but they're all dependabot commits.

I have amended my commit accordingly 👍

[prestist]

@mhutter I understand the confusion lol. We do handle our dependabot prs a bit differently. Ok everything looks great, thank you again, and you have my approval!

[1player]

@apricote Any idea when we'll be able to provision CoreOS cloud or dedicated images at Hetzner? I'd really like to migrate my servers.

[apricote]

@apricote Any idea when we'll be able to provision CoreOS cloud or dedicated images at Hetzner? I'd really like to migrate my servers.

Please see this comment: coreos/fedora-coreos-tracker#1324 (comment)

[1player]

I'm not sure what that linked comment says, honestly. Seems like the CoreOS engineers need information about the Hetzner platform, which I believe Hetzner should provide, not a regular end-user like me.

I just wanted to express my interest, not be the one to open PRs and do the work for Hetzner ;)