repurpose 5.6.x branch to provide local docs build

* remove unused workflows, scripts, and configuration (now handled by docs-build branch)
* upgrade Antora to 3.1 (and Node.js to 16)
* tune playbook settings
* reconfigure docs build for local build only
* add patch to support using linked worktree as Antora content source
* remove Antora extensions not needed for local builds

.github/actions/algolia-config.json

@@ -1,20 +0,0 @@
-{
-  "index_name": "security-docs",
-  "start_urls": [
-    "https://docs.spring.io/spring-security/reference/"
-  ],
-  "selectors": {
-    "lvl0": {
-      "selector": "//nav[@class='crumbs']//li[@class='crumb'][last()-1]",
-      "type": "xpath",
-      "global": true,
-      "default_value": "Home"
-    },
-    "lvl1": ".doc h1",
-    "lvl2": ".doc h2",
-    "lvl3": ".doc h3",
-    "lvl4": ".doc h4",
-    "text": ".doc p, .doc td.content, .doc th.tableblock"
-  }
-}
-

.github/actions/algolia-deploy.sh

@@ -1,20 +0,0 @@
-#!/bin/bash
-
-HOST="$1"
-HOST_PATH="$2"
-SSH_PRIVATE_KEY="$3"
-SSH_KNOWN_HOST="$4"
-
-
-if [ "$#" -ne 4 ]; then
-  echo -e "not enough arguments USAGE:\n\n$0 \$HOST \$HOST_PATH \$SSH_PRIVATE_KEY \$SSH_KNOWN_HOSTS \n\n" >&2
-  exit 1
-fi
-
-# Use a non-default path to avoid overriding when testing locally
-SSH_PRIVATE_KEY_PATH=~/.ssh/github-actions-docs
-install -m 600 -D /dev/null "$SSH_PRIVATE_KEY_PATH"
-echo "$SSH_PRIVATE_KEY" > "$SSH_PRIVATE_KEY_PATH"
-echo "$SSH_KNOWN_HOST" > ~/.ssh/known_hosts
-rsync --delete -avze "ssh -i $SSH_PRIVATE_KEY_PATH" docs/build/site/ "$HOST:$HOST_PATH"
-rm -f "$SSH_PRIVATE_KEY_PATH"

.github/actions/algolia-docsearch-scraper.sh

@@ -1,21 +0,0 @@
-#!/bin/bash
-
-###
-# Docs
-# config.json https://docsearch.algolia.com/docs/config-file
-# Run the crawler https://docsearch.algolia.com/docs/run-your-own/#run-the-crawl-from-the-docker-image
-
-### USAGE
-if [ "$#" -ne 3 ]; then
-  echo -e "not enough arguments USAGE:\n\n$0 \$ALGOLIA_APPLICATION_ID \$ALGOLIA_API_KEY \$CONFIG_FILE\n\n" >&2
-  exit 1
-fi
-
-# Script Parameters
-APPLICATION_ID=$1
-API_KEY=$2
-CONFIG_FILE=$3
-
-#### Script
-script_dir=$(dirname $0)
-docker run -e "APPLICATION_ID=$APPLICATION_ID" -e "API_KEY=$API_KEY" -e "CONFIG=$(cat $CONFIG_FILE | jq -r tostring)" algolia/docsearch-scraper

.github/workflows/algolia-index.yml

@@ -1,20 +0,0 @@
-name: Update Algolia Index
-
-on:
-  schedule:
-    - cron: '0 10 * * *' # Once per day at 10am UTC
-  workflow_dispatch: # Manual trigger
-
-permissions:
-  contents: read
-
-jobs:
-  update:
-    name: Update Algolia Index
-    runs-on: ubuntu-latest
-    if: ${{ github.repository == 'spring-projects/spring-security' }}
-    steps:
-      - name: Checkout Source
-        uses: actions/checkout@v2
-      - name: Update Index
-        run: ${GITHUB_WORKSPACE}/.github/actions/algolia-docsearch-scraper.sh "${{ secrets.ALGOLIA_APPLICATION_ID }}" "${{ secrets.ALGOLIA_WRITE_API_KEY }}" "${GITHUB_WORKSPACE}/.github/actions/algolia-config.json"

.github/workflows/deploy-reference.yml

@@ -1,34 +0,0 @@
-name: Build & Deploy Reference
-
-on:
-  repository_dispatch:
-    types: request-build-reference
-  schedule:
-    - cron: '0 10 * * *' # Once per day at 10am UTC
-  workflow_dispatch: # Manual trigger
-
-permissions:
-  contents: read
-
-jobs:
-  deploy:
-    name: deploy
-    runs-on: ubuntu-latest
-    if: ${{ github.repository == 'spring-projects/spring-security' }}
-    steps:
-      - uses: actions/checkout@v2
-      - name: Set up gradle
-        uses: spring-io/spring-gradle-build-action@v1
-        with:
-          java-version: '11'
-          distribution: 'adopt'
-      - name: Cleanup Gradle Cache
-        # Remove some files from the Gradle cache, so they aren't cached by GitHub Actions.
-        # Restoring these files from a GitHub Actions cache might cause problems for future builds.
-        run: |
-          rm -f /home/runner/.gradle/caches/modules-2/modules-2.lock
-          rm -f /home/runner/.gradle/caches/modules-2/gc.properties
-      - name: Build with Gradle
-        run: ./gradlew :spring-security-docs:antora --stacktrace
-      - name: Deploy
-        run: ${GITHUB_WORKSPACE}/.github/actions/algolia-deploy.sh "${{ secrets.DOCS_USERNAME }}@${{ secrets.DOCS_HOST }}" "/opt/www/domains/spring.io/docs/htdocs/spring-security/reference/" "${{ secrets.DOCS_SSH_KEY }}" "${{ secrets.DOCS_SSH_HOST_KEY }}"