This add support for `plan` input variable and passes it down to the
relevant, inner templates.

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Refs https://gitlab.com/components/opentofu/-/issues/35

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The default rules of the `fmt` job are now empty by default and only set
in the opinionated pipeline templates.

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Sorry, I missed this one when I updated the validate-plan-destroy template.

Similar to !153 this adds support for job name prefixes when using these templates.

This adds a new `job_name_prefix` input, the same as the `job-templates.yml` file so that this can be used mutiple times in the same config, for example to support multi-environment pipelines.

We cannot use it because of
https://gitlab.com/gitlab-org/gitlab/-/issues/477707

Refs https://gitlab.com/components/opentofu/-/issues/34

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Closes https://gitlab.com/components/opentofu/-/issues/23

The ref name may include slashes indicating directories
in a filename and as such we would have to pre-created those
which we do not want. The filename does not matter,
thus, the SHA is as good.