Antora migration (#323)

* Updates maven to 3.9.0

* Migrate Structure

* Insert explicit ids for headers

* Remove unnecessary asciidoc attributes

* Copy default antora files

* Fix indentation for all pages

* Split files

* Generate a default navigation

* Remove includes

* Fix cross references

* Enable Section Summary TOC for small pages

* More antora customization

.github/workflows/deploy-docs.yml

@@ -0,0 +1,32 @@
+name: Deploy Docs
+on:
+  push:
+    branches-ignore: [ gh-pages ]
+    tags: '**'
+  repository_dispatch:
+    types: request-build-reference # legacy
+  #schedule:
+  #- cron: '0 10 * * *' # Once per day at 10am UTC
+  workflow_dispatch:
+permissions:
+  actions: write
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    # if: github.repository_owner == 'spring-cloud'
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          ref: docs-build
+          fetch-depth: 1
+      - name: Dispatch (partial build)
+        if: github.ref_type == 'branch'
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: gh workflow run deploy-docs.yml -r $(git rev-parse --abbrev-ref HEAD) -f build-refname=${{ github.ref_name }}
+      - name: Dispatch (full build)
+        if: github.ref_type == 'tag'
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: gh workflow run deploy-docs.yml -r $(git rev-parse --abbrev-ref HEAD)