title: how to get current user details with WaterfallDialog?
body: <p>I am trying to get current loggedin user details with WaterfallDialog.</p>
  <pre><code>async def _show_members(
      self, turn_context: TurnContext
  ):
      member = await TeamsInfo.get_member(turn_context, turn_context.activity.from_property.id)
  </code></pre>
  <p>I have tried this but its giving this error</p>
  <blockquote>
  <p>[on_turn_error] unhandled error: 'WaterfallStepContext' object has no attribute 'activity'</p>
  </blockquote>
  <blockquote>
  <p>get_team_id
  channel_data = TeamsChannelData(**turn_context.activity.channel_data)
  AttributeError: 'WaterfallStepContext' object has no attribute 'activity'
  Datetime with no tzinfo will be considered UTC.</p>
  </blockquote>