feat: better download for conversation traffic heatmap (#6755)

* feat: genearte report in a grid

* refactor: update API usage

* refactor: separate generate method

* refactor: abstract transform_data

* feat: annotate with comments

* feat: add explicit timezone

* feat: download data only in user timezone

* fix: dates included in heatmap

app/javascript/dashboard/api/reports.js

@@ -59,9 +59,9 @@ class ReportsAPI extends ApiClient {
     });
   }
 
-  getConversationTrafficCSV({ from: since, to: until }) {
+  getConversationTrafficCSV() {
     return axios.get(`${this.url}/conversation_traffic`, {
-      params: { since, until },
+      params: { timezone_offset: getTimeOffset() },
     });
   }