Subscribe to surplus auction updates

[LukSteib]

Goal

Update surplus auctions

Context

The issue is a subset of the implementation proposal you can find here

Work should be done inside surplus.ts

Tasks

• Create a function to subscribe to auction updates subscribeToSurplusAuctions(network, callback)
  • execute fetchCurrentSurplusAuctions
    • return list of auctions via callback(auctions)
  • subscribe via websocket to new events
    • as soon as there is new event, execute fetchSurplusAuctionByIndex to refetch related auction
      • return auction via callback([auction])