Document intl as a required extension

docs/simplesamlphp-install.md

@@ -21,7 +21,7 @@ Prerequisites
  * A web server capable of executing PHP scripts.
  * PHP version >= 7.2.0.
  * Support for the following PHP extensions:
-   * Always required: `date`, `dom`, `hash`, `libxml`, `openssl`, `pcre`, `SPL`, `zlib`, `json`, `mbstring`
+   * Always required: `date`, `dom`, `hash`, `intl`, `json`, `libxml`, `mbstring`, `openssl`, `pcre`, `SPL`, `zlib`
    * When automatically checking for latest versions, and used by some modules: `cURL`
    * When authenticating against an LDAP server: `ldap`
    * When authenticating against a RADIUS server: `radius`

modules/admin/lib/Controller/Config.php

@@ -238,6 +238,12 @@ class Config
                     'required' => Translate::noop('Regular expression support'),
                 ]
             ],
+            'intl_get_error_code' => [
+                'required' => 'required',
+                'descr' => [
+                    'required' => Translate::noop('PHP intl extension'),
+                ]
+            ],
             'json_decode' => [
                 'required' => 'required',
                 'descr' => [