message: Enable token request for HostingSignupDialog
  Needed for the last part of setup which is triggering
  a migration process to the new host.
diff: @@ -49,6 +49,9 @@ export default class HostingSignupDialog extends React.PureComponent<IProps, ISt
  }
  switch (message.data.action) {
  + case 'access_token_credential_request':
  + this.sendAccessToken();
  + break;
  case 'openid_credentials_request':
  // noinspection JSIgnoredPromiseFromCall
  this.fetchOpenIDToken();
  @@ -100,6 +103,13 @@ export default class HostingSignupDialog extends React.PureComponent<IProps, ISt
  }
  }
  + private sendAccessToken() {
  + this.sendMessage({
  + action: 'access_token_credential',
  + token: MatrixClientPeg.get().getAccessToken(),
  + });
  + }
  +
  public componentDidMount() {
  window.addEventListener("message", this.messageHandler);
  }
  