…into add_nullable_to_validation_map

* 'autorestv3' of https://github.com/Azure/autorest.python: (59 commits)
  Support other auth policies (#686)
  correct return type for head operations (#680)
  update mypy.ini (#670)
  import models in operation group if there are just enums (#676)
  add type annotation for empty class model definitions in service client (#672)
  add type ignore to patch file import (#671)
  don't generate namespace test when generating individual swaggers (#683)
  Update package.json
  Update ChangeLog.md
  Fix stdin passthrough when running start.py through run-python3 (#678)
  update to latest testserver (#673)
  Add unicode test routes (#668)
  Generate correct docstrings for paging and LRO operations (#652)
  add missing license headers (#667)
  LRO Continuation Token [need azure-core 1.6.0] (#565)
  fix http request verb to always be get for next operation if not defined (#664)
  Fix generation of pkgutil files (#661)
  deal with optional return types correctly (#656)
  include new testserver test for paging model whose item name has an x-ms-client-name (#654)
  added generating wiki to readme for better access (#646)
  ...