added comment section on card details to avoid loading the card comment activities from the server

- and added to show only the activities a card

- to display the card comments a connection to the server was needed to get the activities of the card comments, now, it's not necessary
- also performance relevant. until now there were a lot of activities loaded, now only of the current card

models/cards.js

@@ -473,6 +473,10 @@ Cards.attachSchema(
       optional: true,
       defaultValue: 0,
     },
+    showActivities: {
+      type: Boolean,
+      defaultValue: false,
+    },
   }),
 );
 
@@ -2167,6 +2171,14 @@ Cards.mutations({
     }
   },
 
+  toggleShowActivities() {
+    return {
+      $set: {
+        showActivities: !this.showActivities,
+      }
+    };
+  },
+
   setCustomField(customFieldId, value) {
     // todo
     const index = this.customFieldIndex(customFieldId);