Correction bug #18 - add a unique constraint - add the original tag to the list (to be able to diffeerentiate) - return 400 bad request when necessary - catch that in the js to display an error message

CREATE DATABASE hdabo
  WITH ENCODING='UTF8'
       OWNER=iri
       TEMPLATE=template0
       LC_COLLATE='fr_FR.UTF-8'
       LC_CTYPE='fr_FR.UTF-8'
       CONNECTION LIMIT=-1;