ci: add workflow to trigger refresh of dependants when a blocking pr is merged

Signed-off-by: Rachel Powers <508861+Ryex@users.noreply.github.com>

.github/workflows/merge_blocking_pr.yml

@@ -0,0 +1,80 @@
+name: Merged Blocking Pull Request Automation
+
+on:
+  pull_request:
+    types:
+      - closed
+
+jobs:
+  update_blocked_status:
+    name: Update Blocked Status
+    runs-on: ubuntu-latest
+
+    if: github.event.pull_request.merged == true
+
+    permissions:
+      issues: write
+      pull-requests: write
+      statuses: write
+      checks: write
+
+    steps:
+      - name: Gather Dependent PRs
+        id: gather_deps
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+
+        run: |
+          owner="${{ github.repository_owner }}"
+          owner_repo="${{ github.repository }}"
+          repo="${owner_repo#"${owner}/"}"
+          blocked_prs=$(
+            gh api graphql \
+              -f repo="$repo" \
+              -f owner="$owner" \
+              -f query='
+                query($repo: String!, $owner: String!,  $endCursor: String) {
+                  repository(name: $repo, owner: $owner) {
+                    pullRequests(first: 100, after: $endCursor, states: [OPEN], labels: ["blocked"]) {
+                      nodes {
+                        number
+                        bodyText
+                        merged
+                      }
+                      pageInfo {
+                        hasNextPage
+                        endCursor
+                      }
+                    }
+                  }
+                }
+              ' \
+              --paginate \
+              --slurp \
+              | jq --argjson pr "${{ github.event.pull_request.number }}" '
+                  [.[].data.repository.pullRequests.nodes[]] | .[] | select(
+                    .bodyText |  
+                      scan("(?:blocked (?:by|on)|stacked on):? #(?<num>[0-9]+)") |
+                      map(tonumber) |
+                      any(.[]; . == $pr)
+                  )
+                '
+          )
+          echo "deps=$blocked_prs" >> "$GITHUB_OUTPUT"
+          echo "numdeps='$(jq -r '. | length' <<< "$blocked_prs")"
+
+      - name: Trigger Blocked PP Workflows for Dependants
+        if: fromJSON(steps.gather_deps.outputs.numdeps) > 0
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          while read -r pr ; do
+            gh api \
+              --method POST \
+              -H "Accept: application/vnd.github+json" \
+              -H "X-GitHub-Api-Version: 2022-11-28" \
+              "/repos/${{ github.repository }}/actions/workflows/blocked_prs.yml/dispatches" \
+              -f "ref=${{ github.ref_name }}" \
+              -f "inputs[pr_id]=$pr"
+          done < <(jq -c '.[].number' <<< "${{steps.gather_deps.outputs.deps}}")
+