ci(e2e): add org membership check to e2e-staging workflow

Author: jacekradko

.github/workflows/e2e-staging.yml

@@ -37,8 +37,33 @@ concurrency:
   cancel-in-progress: true
 
 jobs:
+  permissions-check:
+    name: Check Permissions
+    runs-on: 'blacksmith-8vcpu-ubuntu-2204'
+    steps:
+      - name: Check org membership
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const org = context.repo.owner;
+            const username = context.actor;
+
+            try {
+              const { status } = await github.rest.orgs.checkMembershipForUser({
+                org,
+                username,
+              });
+
+              if (status !== 204) {
+                core.setFailed(`User '${username}' is not a member of the '${org}' organization.`);
+              }
+            } catch (error) {
+              core.setFailed(`User '${username}' is not a member of the '${org}' organization.`);
+            }
+
   validate-instances:
     name: Validate Staging Instances
+    needs: [permissions-check]
     runs-on: 'blacksmith-8vcpu-ubuntu-2204'
     steps:
       - name: Checkout Repo
@@ -56,6 +81,7 @@ jobs:
 
   integration-tests:
     name: Integration Tests (${{ matrix.test-name }}, ${{ matrix.test-project }})
+    needs: [permissions-check]
     runs-on: 'blacksmith-8vcpu-ubuntu-2204'
     defaults:
       run: