Add LDAP STS tests and workflow for CI (#13576)

Runs LDAP tests with openldap container on GH Actions

.github/workflows/ldap-integration.yaml

@@ -0,0 +1,45 @@
+name: External IDP Integration Tests
+
+on:
+  pull_request:
+    branches:
+    - master
+
+# This ensures that previous jobs for the PR are cancelled when the PR is
+# updated.
+concurrency: 
+  group: ${{ github.workflow }}-${{ github.head_ref }}
+  cancel-in-progress: true
+
+jobs:
+  ldap-test:
+    name: LDAP Tests with Go ${{ matrix.go-version }}
+    runs-on: ubuntu-latest
+
+    services:
+      openldap:
+        image: quay.io/minio/openldap
+        ports:
+          - 389:389
+          - 636:636
+        env:
+          LDAP_ORGANISATION: "MinIO Inc"
+          LDAP_DOMAIN: "min.io"
+          LDAP_ADMIN_PASSWORD: "admin"
+
+
+    strategy:
+      matrix:
+        go-version: [1.16.x, 1.17.x]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-go@v2
+        with:
+          go-version: ${{ matrix.go-version }}
+      - name: Test LDAP
+        env:
+          LDAP_TEST_SERVER: "localhost:389"
+        run: |
+          sudo sysctl net.ipv6.conf.all.disable_ipv6=0
+          sudo sysctl net.ipv6.conf.default.disable_ipv6=0
+          make test-ldap