Support video views/viewers stats in server

* Add "currentTime" and "event" body params to view endpoint
 * Merge watching and view endpoints
 * Introduce WatchAction AP activity
 * Add tables to store viewer information of local videos
 * Add endpoints to fetch video views/viewers stats of local videos
 * Refactor views/viewers handlers
 * Support "views" and "viewers" counters for both VOD and live videos

server/lib/activitypub/local-video-viewer.ts

@@ -0,0 +1,42 @@
+import { Transaction } from 'sequelize'
+import { LocalVideoViewerModel } from '@server/models/view/local-video-viewer'
+import { LocalVideoViewerWatchSectionModel } from '@server/models/view/local-video-viewer-watch-section'
+import { MVideo } from '@server/types/models'
+import { WatchActionObject } from '@shared/models'
+import { getDurationFromActivityStream } from './activity'
+
+async function createOrUpdateLocalVideoViewer (watchAction: WatchActionObject, video: MVideo, t: Transaction) {
+  const stats = await LocalVideoViewerModel.loadByUrl(watchAction.id)
+  if (stats) await stats.destroy({ transaction: t })
+
+  const localVideoViewer = await LocalVideoViewerModel.create({
+    url: watchAction.id,
+    uuid: watchAction.uuid,
+
+    watchTime: getDurationFromActivityStream(watchAction.duration),
+
+    startDate: new Date(watchAction.startTime),
+    endDate: new Date(watchAction.endTime),
+
+    country: watchAction.location
+      ? watchAction.location.addressCountry
+      : null,
+
+    videoId: video.id
+  })
+
+  await LocalVideoViewerWatchSectionModel.bulkCreateSections({
+    localVideoViewerId: localVideoViewer.id,
+
+    watchSections: watchAction.watchSections.map(s => ({
+      start: s.startTimestamp,
+      end: s.endTimestamp
+    }))
+  })
+}
+
+// ---------------------------------------------------------------------------
+
+export {
+  createOrUpdateLocalVideoViewer
+}