v0.39.0

• bigtable:
  • Implement DeleteInstance in bttest.
  • Return an error on invalid ReadRowsRequest.RowRange key ranges in bttest.
• bigquery:
  • Move RequirePartitionFilter outside of TimePartioning.
  • Expose models API.
• firestore:
  • Allow array values in create and update calls.
  • Add CollectionGroup method.
• pubsub:
  • Add ExpirationPolicy to Subscription.
• storage:
  • Add V4 signing.
• rpcreplay:
  • Match streams by first sent request. This further improves rpcreplay's
    ability to distinguish streams.
• httpreplay:
  • Set up Man-In-The-Middle config only once. This should improve proxy
    creation when multiple proxies are used in a single process.
  • Remove error on empty Content-Type, allowing requests with no Content-Type
    header but a non-empty body.
• all:
  • Fix an edge case bug in auto-generated library pagination by properly
    propagating pagetoken.