re-design automatic cargo dependency upgrades: collect all patch releases and make only one pull request for them per week

.github/dependabot.yml

@@ -1,11 +1,27 @@
 version: 2
 updates:
+  # upgrade cargo patch versions once per week
+  # see `workflows/upgrade.yml`
+
+  # major and minor cargo upgrades only once per week
   - package-ecosystem: "cargo"
     directory: "/"
     schedule:
-      interval: "daily"
+      interval: "weekly"
+      day: "monday"
+      time: "06:00"
+      timezone: "Europe/Berlin"
+    groups:
+      weekly-patch-updates:
+        applies-to: "version-updates"
+        patterns:
+          - "*"
+        update-types:
+          - "major"
+          - "minor"
     # open-pull-requests-limit: 0 # temporarily disable dependabot
 
+  # upgrade all GitHub Actions soon
   - package-ecosystem: "github-actions"
     directory: "/"
     schedule:

.github/workflows/cargo-update.yml

@@ -0,0 +1,68 @@
+name: Cargo Update
+
+on:
+  workflow_dispatch:
+
+  schedule:
+    - cron: "23 4 * * 1"
+
+concurrency:
+  group: cargo-update
+  cancel-in-progress: false
+
+jobs:
+  cargo-update:
+    name: Update Cargo dependencies
+    runs-on: ubicloud-standard-2
+
+    permissions:
+      contents: write
+      pull-requests: write
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+          ref: main
+          fetch-depth: 0 # fetch entire git history
+
+      - name: cargo update
+        run: cargo update --verbose
+      - name: Validate updated lockfile
+        run: cargo metadata --locked --no-deps > /dev/null
+      - name: cargo vet regenerate exemptions
+        run: cargo vet regenerate exemptions
+
+      - name: Create pull request
+        uses: peter-evans/create-pull-request@v8
+        with:
+          token: ${{ secrets.CARGO_UPDATE_TOKEN || github.token }}
+
+          base: main
+          branch: automation/cargo-update
+          delete-branch: true
+
+          add-paths: |
+            Cargo.lock
+            supply-chain/
+
+          commit-message: "chore(deps): cargo update"
+          title: "chore(deps): cargo update"
+
+          body: |
+            This pull request was generated automatically by GitHub Workflow `Cargo Update`.
+
+            It executes:
+
+            ```bash
+            cargo update
+            cargo vet regenerate exemptions
+            ```
+
+          labels: |
+            dependencies
+            rust
+            maintenance
+
+          draft: false