Switch to the new "Prepare release" GitHub Actions workflow

Switches to the new shared workflow added in:
heroku/languages-github-actions#184

GUS-W-14900211.

.github/workflows/hatchet_app_cleaner.yml

@@ -1,4 +1,4 @@
-name: Hatchet app cleaner
+name: Hatchet App Cleaner
 
 on:
   schedule:

.github/workflows/prepare-release.yml

@@ -1,76 +1,8 @@
-name: Prepare release
+name: Prepare Release
 
 on: workflow_dispatch
 
 jobs:
   prepare-release:
-    name: Prepare Release
-    runs-on: pub-hk-ubuntu-22.04-small
-    steps:
-      - name: Get token for GH application (Linguist)
-        uses: heroku/use-app-token-action@main
-        id: generate-token
-        with:
-          app_id: ${{ vars.LINGUIST_GH_APP_ID }}
-          private_key: ${{ secrets.LINGUIST_GH_PRIVATE_KEY }}
-
-      - name: Checkout
-        uses: actions/checkout@v4
-        with:
-          # We always want the version bump/changelog and resultant PR to target main, not the branch of the workflow_dispatch.
-          ref: main
-          # Using the GH application token here will configure the local git config for this repo with credentials
-          # that can be used to make signed commits that are attributed to the GH application user
-          token: ${{ steps.generate-token.outputs.app_token }}
-
-      - name: Determine existing published version
-        id: existing-version
-        # This uses the buildpack registry API directly instead of the Heroku CLI, since the latter
-        # requires being logged in for version queries even though the registry API itself doesn't.
-        run: |
-          URI_ENCODED_BUILDPACK_NAME='heroku%2Fpython'
-          VERSION=$(
-            curl --silent --show-error --fail --retry 3 --retry-connrefused --connect-timeout 10 \
-                -H 'Accept: application/vnd.heroku+json; version=3.buildpack-registry' \
-                "https://buildpack-registry.heroku.com/buildpacks/${URI_ENCODED_BUILDPACK_NAME}/revisions" \
-              | jq --exit-status --raw-output 'max_by(.release) | .release'
-          )
-          echo "version=${VERSION}" >> "${GITHUB_OUTPUT}"
-
-      - name: Calculate new version
-        id: new-version
-        run: echo "version=$((${{ steps.existing-version.outputs.version }}+1))" >> "${GITHUB_OUTPUT}"
-
-      - name: Update changelog
-        run: |
-          EXISTING_VERSION='${{ steps.existing-version.outputs.version }}'
-          NEW_VERSION='${{ steps.new-version.outputs.version }}'
-          DATE_TODAY="$(date --utc --iso-8601)"
-          UNRELEASED_URL="https://github.com/${{ github.repository }}/compare/v${NEW_VERSION}...HEAD"
-          NEW_VERSION_URL="https://github.com/${{ github.repository }}/compare/v${EXISTING_VERSION}...v${NEW_VERSION}"
-
-          sed --in-place --regexp-extended \
-            --expression "s~(^## \[Unreleased\])$~\1\n\n\n## [v${NEW_VERSION}] - ${DATE_TODAY}~" \
-            --expression "s~(^\[unreleased\]:) .*$~\1 ${UNRELEASED_URL}\n[v${NEW_VERSION}]: ${NEW_VERSION_URL}~" \
-            CHANGELOG.md
-    
-      - name: Create pull request
-        id: pr
-        uses: peter-evans/[email protected]
-        with:
-          token: ${{ steps.generate-token.outputs.app_token }}
-          title: Prepare release v${{ steps.new-version.outputs.version }}
-          body: |
-            Changes:
-            https://github.com/${{ github.repository }}/compare/v${{ steps.existing-version.outputs.version }}...main
-          commit-message: Prepare release v${{ steps.new-version.outputs.version }}
-          branch: prepare-release
-          delete-branch: true
-          committer: ${{ vars.LINGUIST_GH_APP_USERNAME }} <${{ vars.LINGUIST_GH_APP_EMAIL }}>
-          author: ${{ vars.LINGUIST_GH_APP_USERNAME }} <${{ vars.LINGUIST_GH_APP_EMAIL }}>
-
-      - name: Configure pull request
-        if: steps.pr.outputs.pull-request-operation == 'created'
-        run: gh pr merge --auto --squash "${{ steps.pr.outputs.pull-request-number }}"
-        env:
-          GH_TOKEN: ${{ steps.generate-token.outputs.app_token }}
+    uses: heroku/languages-github-actions/.github/workflows/_classic-buildpack-prepare-release.yml@latest
+    secrets: inherit