chore(workflow): implement conditional approval check for major releases

Author: cy-yun

.github/workflows/major-version-approval.yaml

@@ -0,0 +1,53 @@
+name: Major Version Approval Check
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, edited]
+    branches: ['main']
+  pull_request_review:
+    types: [submitted]
+
+permissions:
+  contents: read
+  pull-requests: read
+
+jobs:
+  major-version-approval-check:
+    name: Major Version Approval Check
+    runs-on: ubuntu-latest
+    if: github.event.pull_request.user.login == 'release-please[bot]' && contains(github.event.pull_request.body, 'MAJOR_VERSION_ALLOWED=')
+    steps:
+      - name: Check for at least 2 approvals from yoshi-php members
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          PR_NUMBER: ${{ github.event.pull_request.number }}
+          REQUIRED_APPROVALS: 2
+        run: |
+          set -eo pipefail
+
+          echo "Fetching approvals for PR #$PR_NUMBER..."
+          # Get a unique, sorted list of all users who have approved.
+          approvals=$(gh pr view $PR_NUMBER --json reviews --jq '[.reviews[] | select(.state == "APPROVED") | .author.login] | unique | .[]' | sort -u)
+          if [ -z "$approvals" ]; then
+            echo "No approvals found on this PR."
+            approvals=""
+          fi
+
+          echo "Fetching yoshi-php team members..."
+          team_members=$(gh api --paginate orgs/googleapis/teams/yoshi-php/members --jq '.[].login' | sort -u)
+          if [ -z "$team_members" ]; then
+            echo "Error: Could not fetch any members for the yoshi-php team."
+            exit 1
+          fi
+
+          # find and count the intersection of the two lists.
+          count=$(echo "$team_members" | grep -F -x -f <(echo "$approvals") | wc -l)
+
+          echo "Found $count approval(s) from the yoshi-php team."
+
+          if [[ $count -lt $REQUIRED_APPROVALS ]]; then
+            echo "Error: Requires at least $REQUIRED_APPROVALS approvals from the yoshi-php team. Only $count found."
+            exit 1
+          else
+            echo "Success: Approval requirement of $REQUIRED_APPROVALS met."
+          fi