converse-roster: dedupe group names

src/headless/plugins/roster/contact.js

@@ -12,6 +12,7 @@ const { Strophe, $iq, $pres } = converse.env;
 const RosterContact = Model.extend({
     defaults: {
         'chat_state': undefined,
+        'groups': [],
         'image': _converse.DEFAULT_IMAGE,
         'image_type': _converse.DEFAULT_IMAGE_TYPE,
         'num_unread': 0,
@@ -25,7 +26,6 @@ const RosterContact = Model.extend({
         const bare_jid = Strophe.getBareJidFromJid(jid).toLowerCase();
         attributes.jid = bare_jid;
         this.set(Object.assign({
-            'groups': [],
             'id': bare_jid,
             'jid': bare_jid,
             'user_id': Strophe.getNodeFromJid(jid)

src/headless/plugins/roster/contacts.js

@@ -299,7 +299,7 @@ const RosterContacts = Collection.extend({
         const contact = this.get(jid);
         const subscription = item.getAttribute("subscription");
         const ask = item.getAttribute("ask");
-        const groups = Array.from(item.getElementsByTagName('group')).map(e => e.textContent);
+        const groups = [...new Set(sizzle('group', item).map(e => e.textContent))];
         if (!contact) {
             if ((subscription === "none" && ask === null) || (subscription === "remove")) {
                 return; // We're lazy when adding contacts.