fix: pass proper ref to metadata-action

[volmedo]

When not using a custom value, docker/metadata-action takes the ref from github.ref. However, the value of that is refs/heads/main when the workflow is triggered by workflow_run. That cannot be parsed into a semver, and the result is no tags in metadata, which then makes the docker push fail.

The fix is to extract the value from what the Determine ref step determines (which is the one that Releaser inferred from version.json). A match regex is also provided so that both v1.2.3 (what we will get when workflow_run) and refs/tags/v1.2.3 (what we will get when pushing a tag) work.

[codecov]

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