Fix handling of advmutltiselect (on localization form) Add deprecatio…

…n notice rather than hard-fail for incorrect case for html type.

We have clarified the correct syntax (it was haphazard) an updated the docs.

This ALSO fixes fails on localisation form

CRM/Admin/Form/SettingTrait.php

@@ -219,8 +219,17 @@ protected function addFieldsDefinedInSettingsMetadata() {
   protected function getQuickFormType($spec) {
     if (isset($spec['quick_form_type']) &&
     !($spec['quick_form_type'] === 'Element' && !empty($spec['html_type']))) {
+      // This is kinda transitional
       return $spec['quick_form_type'];
     }
+
+    // The spec for settings has been updated for consistency - we provide deprecation notices for sites that have
+    // not made this change.
+    $htmlType = $spec['html_type'];
+    if ($htmlType !== strtolower($htmlType)) {
+      CRM_Core_Error::deprecatedFunctionWarning(ts('Settings fields html_type should be lower case - see https://docs.civicrm.org/dev/en/latest/framework/setting/ - this needs to be fixed for ' . $spec['name']));
+      $htmlType = strtolower($spec['html_type']);
+    }
     $mapping = [
       'checkboxes' => 'CheckBoxes',
       'checkbox' => 'CheckBox',
@@ -229,8 +238,9 @@ protected function getQuickFormType($spec) {
       'textarea' => 'Element',
       'text' => 'Element',
       'entity_reference' => 'EntityRef',
+      'advmultiselect' => 'Element',
     ];
-    return $mapping[$spec['html_type']];
+    return $mapping[$htmlType];
   }
   /**
    * Get the defaults for all fields defined in the metadata.