Add tofu plan and validate workflows for pull requests

Split into two workflows:

- validate.yaml: runs on pull_request (no secrets needed), does
  tofu init -backend=false + tofu validate for immediate feedback
  on syntax/config errors.

- plan.yaml: runs on pull_request_target with a required "plan"
  environment gate, so a maintainer must approve before secrets
  (AWS creds, GitHub App token) are exposed to the PR's code.
  Posts the plan output as a PR comment.

The environment gate mitigates the Pwn Request risk inherent in
pull_request_target + checkout PR head: external data sources and
provider binaries execute during plan, so untrusted code must not
run without human review of the diff.

Assisted-by: Claude Code <noreply@anthropic.com>
Signed-off-by: Riccardo Piccoli <rpiccoli@redhat.com>

Author: rccrdpccl

.github/workflows/plan.yaml

@@ -0,0 +1,121 @@
+name: Plan
+
+on:
+  pull_request_target:
+    paths:
+      - "**/*.tf"
+      - "**/*.csv"
+
+permissions:
+  contents: read
+  pull-requests: write
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  plan:
+    runs-on: ubuntu-latest
+    environment: plan
+    env:
+      AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
+      AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
+      CONFIG_APP_CLIENT_ID: Iv23lipEOAvwk5QqNUie
+      TF_CLI_ARGS: "-no-color"
+      TF_IN_AUTOMATION: "true"
+    steps:
+      - name: Checkout PR
+        uses: actions/checkout@v7
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Generate a token
+        id: generate-token
+        uses: actions/create-github-app-token@v3
+        with:
+          client-id: ${{ env.CONFIG_APP_CLIENT_ID }}
+          private-key: ${{ secrets.CONFIG_APP_SECRET }}
+          owner: ${{ github.repository_owner }}
+
+      - name: Setup OpenTofu
+        uses: opentofu/setup-opentofu@v2
+        with:
+          tofu_wrapper: false
+
+      - name: TF init
+        run: tofu init
+
+      - name: TF Validate
+        run: tofu validate
+
+      - name: TF Plan
+        id: plan
+        run: |
+          set +e
+          tofu plan -detailed-exitcode 2>&1 | tee plan_output.txt
+          exitcode=${PIPESTATUS[0]}
+          echo "exitcode=$exitcode" >> "$GITHUB_OUTPUT"
+          if [ "$exitcode" -eq 1 ]; then
+            exit 1
+          fi
+        env:
+          GITHUB_TOKEN: ${{ steps.generate-token.outputs.token }}
+
+      - name: Comment plan on PR
+        if: always() && steps.plan.outcome != 'skipped'
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const fs = require('fs');
+            const raw = fs.readFileSync('plan_output.txt', 'utf8');
+            const plan = raw.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+            const exitcode = '${{ steps.plan.outputs.exitcode }}';
+
+            let summary;
+            if (exitcode === '0') {
+              summary = 'No changes. Infrastructure is up-to-date.';
+            } else if (exitcode === '2') {
+              summary = 'Changes detected. Review the plan below.';
+            } else {
+              summary = 'Plan failed. See details below.';
+            }
+
+            const marker = '<!-- tofu-plan -->';
+            const body = [
+              marker,
+              `### OpenTofu Plan`,
+              '',
+              summary,
+              '',
+              '<details><summary>Show plan output</summary>',
+              '',
+              `<pre>${plan.substring(0, 60000)}</pre>`,
+              '',
+              '</details>',
+              '',
+              `*Commit: ${context.payload.pull_request.head.sha}*`,
+            ].join('\n');
+
+            const { data: comments } = await github.rest.issues.listComments({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: context.issue.number,
+            });
+            const existing = comments.find(c => c.body.includes(marker));
+
+            if (existing) {
+              await github.rest.issues.updateComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                comment_id: existing.id,
+                body,
+              });
+            } else {
+              await github.rest.issues.createComment({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.issue.number,
+                body,
+              });
+            }

.github/workflows/validate.yaml

@@ -0,0 +1,30 @@
+name: Validate
+
+on:
+  pull_request:
+    paths:
+      - "**/*.tf"
+      - "**/*.csv"
+
+permissions:
+  contents: read
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    env:
+      TF_CLI_ARGS: "-no-color"
+      TF_IN_AUTOMATION: "true"
+    steps:
+      - uses: actions/checkout@v7
+
+      - name: Setup OpenTofu
+        uses: opentofu/setup-opentofu@v2
+        with:
+          tofu_wrapper: false
+
+      - name: TF init (no backend)
+        run: tofu init -backend=false
+
+      - name: TF Validate
+        run: tofu validate