Load article LIFF's trend data in hourly cron job and expose them in API

[MrOrz]

GA report query

• filter: ga:eventCategory==ViewArticle;ga:eventAction==LIFF
• primaryDimension: ga:eventLabel, ga:source

Output structure

{
  stats: {
    webUser: number; webVisit: number;
    // existing Cofacts chatbot webhook number
    lineUser: number; lineVisit: number;
    // Breakdown by source. Source can be '' if not specified.
    liff: {source: string; user: number; visit: number}[]
  }
}