refactor(xwiki): move extension installer logic into static Groovy file and switch to plugins dict

- Added 'plugins' section in config/main.yml to declare enabled extensions in a structured way
- Introduced new static file 'files/extension_installer_b64.groovy' that decodes Base64 JSON of requested plugins
- Simplified 04_extensions.yml: now builds installer code from static file and removed hardcoded OIDC/LDAP checks
- Dropped redundant XWIKI_EXT_* variables in vars/main.yml
- Added XWIKI_PLUGINS fact to collect enabled plugin items from config/main.yml

This refactor makes extension installation more generic, easier to unit test, and extendable beyond OIDC/LDAP.

See: https://chatgpt.com/share/68ca25e3-cbc4-800f-a45e-2b152369811a

roles/web-app-xwiki/vars/main.yml

@@ -44,12 +44,6 @@ XWIKI_REST_XWIKI:                     "{{ [XWIKI_REST_BASE, 'wikis/xwiki'] | url
 XWIKI_REST_XWIKI_PAGES:               "{{ [XWIKI_REST_BASE, 'wikis/xwiki/spaces/XWiki/pages'] | url_join }}"
 XWIKI_REST_EXTENSION_INSTALL:         "{{ [XWIKI_REST_BASE, 'jobs'] | url_join }}"
 
-# Extension IDs + Versions (pin versions explicitly)
-XWIKI_EXT_LDAP_ID:                    "org.xwiki.contrib.ldap:ldap-authenticator"
-XWIKI_EXT_LDAP_VERSION:               "9.15.7"
-XWIKI_EXT_OIDC_ID:                    "org.xwiki.contrib.oidc:oidc-authenticator"
-XWIKI_EXT_OIDC_VERSION:               "2.19.2"
-
 # LDAP configuration (mapped to LDAP.* context)
 XWIKI_LDAP_SERVER:                    "{{ LDAP.SERVER.DOMAIN }}"
 XWIKI_LDAP_PORT:                      "{{ LDAP.SERVER.PORT }}"
@@ -71,3 +65,11 @@ XWIKI_OIDC_CLIENT_SECRET:             "{{ OIDC.CLIENT.SECRET }}"
 XWIKI_OIDC_SCOPES:                    "openid email profile {{ RBAC.GROUP.CLAIM }}"
 XWIKI_OIDC_GROUPS_CLAIM:              "{{ RBAC.GROUP.CLAIM }}"
 XWIKI_OIDC_ADMIN_PROVIDER_GROUP:      "{{ [RBAC.GROUP.NAME, XWIKI_ADMIN_GROUP] | path_join }}"
+
+# Collect enabled plugin items from config/main.yml
+XWIKI_PLUGINS: >-
+  {{
+    (applications | get_app_conf(application_id, 'plugins'))
+    | dict2items | selectattr('value.enabled','equalto', true)
+    | map(attribute='value.items') | list | sum(start=[])
+  }}