Require a router_type to validate a record in the endpoint

[bbangert]

Per https://sentry.prod.mozaws.net/operations/autopush-prod/issues/671942/ we should require a router_type in the record or drop it.

Traceback:

KeyError: None
  File "twisted/internet/defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "autopush/web/base.py", line 222, in _validation_err
    fail.trap(InvalidRequest)
  File "twisted/python/failure.py", line 359, in trap
    self.raiseException()
  File "twisted/internet/defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "autopush/web/base.py", line 258, in _boto_err
    fail.trap(BotoServerError)
  File "twisted/python/failure.py", line 359, in trap
    self.raiseException()
  File "twisted/internet/defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "autopush/web/base.py", line 250, in _overload_err
    fail.trap(ProvisionedThroughputExceededException)
  File "twisted/python/failure.py", line 359, in trap
    self.raiseException()
  File "twisted/internet/defer.py", line 653, in _runCallbacks
    current.result = callback(current.result, *args, **kw)
  File "autopush/web/base.py", line 76, in _call_func
    return func(request_handler, **output_kwargs)
  File "autopush/web/webpush.py", line 496, in post
    router = self.routers[router_type]

[pjenvey]

websocket already does this check before validating the current month, it just needs to be brought over to WebPushHandler's validation

[bbangert]

The webpush handler validation does it as well, as long as router_type exists and is set to 'webpush'.

[bbangert]

https://sentry.prod.mozaws.net/operations/autopush-prod/issues/671942/