feat: read HCLOUD_TOKEN from file

[simonostendorf]

This allows the HCLOUD_TOKEN (and ROBOT_USER and ROBOT_PASSWORD) to be read from a file. This can be useful if the token is injected using secret injection (e.g. with the vault agent injector).

I tested the changes on my dev cluster. I cannot test the robot account changes, because I only use hcloud. But because they use the same function inside the code I think its working too :). If someone is interested in using this with the vault agent injector, I used the following helm values:

image:
  repository: <custom-image-because-changes-are-not-released>
  tag: <custom-image-because-changes-are-not-released>
podAnnotations:
  vault.hashicorp.com/agent-inject: "true"
  vault.hashicorp.com/log-format: json
  vault.hashicorp.com/role: <your-vault-role-name>
  vault.hashicorp.com/secret-volume-path-token: /vault/secrets
  vault.hashicorp.com/agent-inject-file-token: token
  vault.hashicorp.com/agent-inject-secret-token: <your-vault-mount>/data/<your-vault-path>
  vault.hashicorp.com/agent-inject-template-token: |
    {{ with secret "<your-vault-mount>/data/<your-vault-path>" -}}
     {{ .Data.data.token }}
    {{- end }}
env:
  HCLOUD_TOKEN_FILE:
    value: "/vault/secrets/token"
  HCLOUD_TOKEN: null # must be set because helm results in using value and valueFrom and that results in an error

This change is inspired from external-dns cloudflare provider. I requested the same change for the csi-driver to keep consistency in reading HCLOUD_TOKEN from file.

Closes #595

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.81%. Comparing base (ed097ab) to head (12ee38b).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #652      +/-   ##
==========================================
+ Coverage   76.23%   76.81%   +0.58%     
==========================================
  Files          21       20       -1     
  Lines        2264     2105     -159     
==========================================
- Hits         1726     1617     -109     
+ Misses        360      329      -31     
+ Partials      178      159      -19     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[jooola]

Overall, the feature looks great, I only have a few nits.

We will have to wait for @apricote for the final merge decision.

[apricote]

Thanks for the PR @simonostendorf!

Dont worry about the e2e tests failing, they dont work for people outside of the hetznercloud organization on GitHub.

[simonostendorf]

I forgot to update the helm chart and i pushed some of my private fixes, sorry. I will fix this as soon as possible :D

[apricote]

Thank you very much @simonostendorf! I pushed a small commit with two style fixes. The e2e tests also were successful locally. Going to merge this now :)