change key from title to id

Duplicate key when title is the same, avoid it using the id as identifier

src/views/feature/Feature_detail.vue

@@ -176,7 +176,7 @@
       <div class="seven wide column">
         <h2 class="ui header">Pièces jointes</h2>
 
-        <div v-for="pj in attachments" :key="pj.title" class="ui divided items">
+        <div v-for="pj in attachments" :key="pj.id" class="ui divided items">
           <div class="item">
             <a
               class="ui tiny image"