frontend: implement event logging and run in parallel

Created by: unknwon

Implement event logging feature requested in https://github.com/sourcegraph/sourcegraph/issues/5486.

Changes in this PR:

• Created DB event_logs and insertion logic
• Updated GraphQL logUserEvent to accept new parameters
• Added a goroutine to delete rows in event_logs after 93 days, and check every hour
• Added a feature flag EventLogging with default enabled

Test plan:

• Unit tests
• Manual testing
  • GraphQL API console

   mutation logEvent($event: String!, $userCookieID: String!, $url: String!, $source: UserEventSource!, $argument: String) {
     logEvent(event: $event, userCookieID: $userCookieID, url: $url, source: $source, argument: $argument) {
       alwaysNil
     }
   }
   		
   {
   	"event": "test_event",
   	"userCookieID": "AAABBBCCCDDD",
   	"url": "http://localhost:3080/api/console",
   	"source": "WEB"
   }

  • Trigger log action via browsing