ci: Add automatic pull request labeler

.github/labeler.yml

@@ -0,0 +1,27 @@
+# Configuration for the Labeler GitHub action, executed by
+# .github/workflows/labeler.yml.
+#
+# The basic syntax is [label]: [path patterns].
+#
+# For more details on the configuration please see:
+# https://github.com/marketplace/actions/labeler
+
+"part:docs": 
+  - "**/*.md"
+  - LICENSE
+
+"part:tests":
+  - "tests/**"
+
+"part:tooling":
+  - ".git*"
+  - ".git*/**"
+  - "**/*.toml"
+  - "**/*.ini"
+  - CODEOWNERS
+  - MANIFEST.in
+  - "*requirements*.txt"
+  - setup.py
+
+"part:channels":
+  - "src/frequenz/channels/**"

.github/workflows/labeler.yml

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+name: Pull Request Labeler
+
+# XXX: !!! SECURITY WARNING !!!
+# pull_request_target has write access to the repo, and can read secrets. We
+# need to audit any external actions executed in this workflow and make sure no
+# checked out code is run (not even installing dependencies, as installing
+# dependencies usually can execute pre/post-install scripts). We should also
+# only use hashes to pick the action to execute (instead of tags or branches).
+# For more details read:
+# https://securitylab.github.com/research/github-actions-preventing-pwn-requests/
+on: [pull_request_target]
+
+jobs:
+  Label:
+    permissions:
+      contents: read
+      pull-requests: write
+    runs-on: ubuntu-latest
+    steps:
+      - name: Labeler
+        # Only use hashes, see the security comment above
+        uses: actions/labeler@e54e5b338fbd6e6cdb5d60f51c22335fc57c401e  # 4.0.1
+        with:
+          repo-token: "${{ secrets.GITHUB_TOKEN }}"