Use action to define "current" version for internal references

[Ilyes512]

Replace hard-coded self referencing version like: example with:

In case it helps anyone, we created a composite action that implements @maxbergs's solution

https://github.com/canonical/get-workflow-version-action

Example usage:

# Reusable workflow (e.g. build_charm.yaml)
on:
  workflow_call:

jobs:
  foo:
    runs-on: ubuntu-latest
    steps:
      - name: Get workflow version
        id: workflow-version
        uses: canonical/get-workflow-version-action@v1
        with:
          repository-name: canonical/data-platform-workflows
          file-name: build_charm.yaml
      # Use the version. For example:
      - name: Install Python CLI
        run: pipx install git+https://github.com/canonical/data-platform-workflows@'${{ steps.workflow-version.outputs.sha }}'#subdirectory=python/cli

Source: actions/toolkit#1264 (comment)