feat: Add support for backport automation

.github/automatic_backport_tracks.yaml

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+automatic_backport_tracks:
+  - track/1.0

.github/workflows/on_pull_request.yaml

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+name: On Pull Request
+
+# On pull_request, we:
+# * create backport labels if it is against main, only when the PR is opened/reopened
+
+on:
+  pull_request:
+
+jobs:
+
+  populate-labels:
+    name: Populate labels
+    if: github.base_ref == 'main' && (github.event.action == 'opened' || github.event.action == 'reopened')
+    uses: canonical/charmed-kubeflow-workflows/.github/workflows/populate-labels.yaml@main
+    secrets: inherit
+    with:
+      track_file_path: ".github/automatic_backport_tracks.yaml"
+      label_prefix: "backport "

.github/workflows/on_pull_request_closed.yaml

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+name: On Pull Request Closed
+
+# When a pull request is pushed on the main branch, automatically
+# create backport PRs according to the labels on the pull request.
+# If there are conflicts, create a PR but leave it as draft.
+
+on:
+  pull_request_target:
+    types: [closed]
+    branches:
+    - main
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+
+  backport:
+    name: Backport pull request
+    if: github.event.pull_request.merged
+    uses: canonical/charmed-kubeflow-workflows/.github/workflows/backport-pr.yaml@main
+    secrets: inherit