XWiki: LDAP/OIDC admin mapping, config mounts, and REST installs

- LDAP: move settings to xwiki.cfg; enable trylocal (1/0), group_mapping to XWiki.XWikiAdminGroup,
  and mode_group_sync=always.
- OIDC: add groups claim request (oidc.userinfoclaims), map provider group to XWiki.XWikiAdminGroup,
  and use space-separated scopes.
- Compose: mount xwiki.cfg and xwiki.properties into /usr/local/xwiki.
- Extensions: wait for REST readiness; pre-check OIDC/LDAP extensions (URL-encoded IDs);
  install via REST job only if missing.
- Vars: strict mappings to LDAP.* and OIDC.* (no defaults), add XWIKI_ADMIN_GROUP and derived DNs.
- Config: expose ldap.local_enabled; tidy meta tags; README grammar update.

Conversation: https://chatgpt.com/share/68c2b8ad-4814-800f-b377-065f967998db

roles/web-app-xwiki/templates/installjobrequest.xml.j2

@@ -0,0 +1,27 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<jobRequest xmlns="http://www.xwiki.org">
+  <id>install-extensions</id>
+  <jobType>install</jobType>
+  <request>
+    <namespace>wiki:xwiki</namespace>
+    <interactive>false</interactive>
+    <verbose>true</verbose>
+    <installDependencies>true</installDependencies>
+    <extensions>
+      {% if XWIKI_LDAP_ENABLED | bool %}
+      <extension>
+        <id>{{ XWIKI_EXT_LDAP_ID }}</id>
+        <version>{{ XWIKI_EXT_LDAP_VERSION }}</version>
+        <namespace>wiki:xwiki</namespace>
+      </extension>
+      {% endif %}
+      {% if XWIKI_OIDC_ENABLED | bool %}
+      <extension>
+        <id>{{ XWIKI_EXT_OIDC_ID }}</id>
+        <version>{{ XWIKI_EXT_OIDC_VERSION }}</version>
+        <namespace>wiki:xwiki</namespace>
+      </extension>
+      {% endif %}
+    </extensions>
+  </request>
+</jobRequest>