Skip automatic deployment job if secrets aren't set (especially for forks)

[ctmbl]

to test it properly i have to push this comit to my main branch on my own fork I also added a smoke test fake secret to test it here

[ctmbl]

EDIT: since https://github.com/iScsc/blog.iscsc.fr/pull/57#issuecomment-2094518836 I had to update this solution because some things were flawed

I've been down the rabbit hole and it seems to be no nice way to do what I want to do here.

TLDR:

• https://github.com/peaceiris/actions-gh-pages/issues/153
• if: github.event.repository.fork == false if: ${{ ! github.event.repository.fork }} (see https://github.com/iScsc/blog.iscsc.fr/pull/57#issuecomment-2094518836) : a poor way to do it (but also the only one...)
• the best way would be to check in env/secrets contexts that needed secrets are defined but:
  • https://github.com/actions/runner/issues/1189
  • https://docs.github.com/en/actions/learn-github-actions/contexts#context-availability ==> env and secrets contexts are not available in jobs.<job_id>.if

Workflow syntax: https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#env