[Story] Testing of release workflow steps on PR creation

[ouphi]

Note: Given the context this story is not a priority and might be overkill - Please align with the repo owners before starting on this story.

Description

The release workflow will not be running often, it only run if a user triggers manually.
There is a risk that this workflow gets broken without us knowing it. For example, if somebody adds a mandatory arg to the basic station Dockerfile, the job building the image would be broken, but we would only notice it when creating a release.

A solution could be:

• Trigger the release workflow on PR
• Disable steps that we only want to happen on a real release. For example pushing images and the release creation would be disabled when the trigger is pull_request.

Acceptance criteria

• The risk to break the release workflow is minimised
• Most of the release workflow is tested on PR.

Tasks

• Add a pull_request trigger
• Disable release creation if the trigger is not workflow_dispatch
• Disable publishing images to docker hub if the trigger is not workflow_dispatch