fix(plugins) Avoid using substr to truncate utf8 data

This avoids JSON encoding errors in the webservice and other bugs
 related to strings getting truncated in the middle of a multibyte character.

issue #5799

argonaut/addons/argonaut/class_argonautQueue.inc

@@ -321,8 +321,8 @@ class argonautQueue extends simpleManagement
     if ($infos) {
       $str = $infos['name'];
 
-      if (strlen($str) > 20) {
-        $str = substr($str, 0, 18)."...";
+      if (mb_strlen($str) > 20) {
+        $str = mb_substr($str, 0, 18)."...";
       }
 
       $str = htmlentities($str, ENT_COMPAT, 'UTF-8');

renater-partage/personal/mail/mail-methods/class_mail-methods-renater-partage.inc

@@ -273,7 +273,7 @@ class mailMethodRenaterPartage extends mailMethod
         }
       }
       $account['zimbraAccountStatus'] = ($mainTab->attributesAccess['userPassword']->isLocked() ? 'locked' : 'active');
-      $account['initials'] = strtoupper(substr($mainTab->givenName, 0, 1).substr($mainTab->sn, 0, 1));
+      $account['initials'] = mb_strtoupper(mb_substr($mainTab->givenName, 0, 1).mb_substr($mainTab->sn, 0, 1));
 
       /* Sync fields from SUPANN if tab is active */
       if (isset($this->parent->parent->by_object['supannAccount']) && $this->parent->parent->by_object['supannAccount']->is_account) {

supann/admin/supannStructures/class_supann.inc

@@ -74,8 +74,8 @@ class supann
   /* return the 64 first chars and "…" after if text is longer */
   static function truncate_label($str, $len = 50)
   {
-    if (strlen($str) > $len) {
-      return substr($str, 0, $len).'…';
+    if (mb_strlen($str) > $len) {
+      return mb_substr($str, 0, $len).'…';
     } else {
       return $str;
     }