MariusButuc

 Change the "Add tags" behaviour :
 - only admins should be able to create new tags,
 - the other users should only be able to add tags from the existing list
#if(!$hasAdmin && !$xwiki.tag.getAllTags().contains($tag))
  #set($result = 'NOT_ALLOWED')
#else
  #set($result = $xwiki.tag.addTagsToDocument($tag, $doc.fullName))
#end
  ...