code: @VisibleForTesting
    String getOverridenHost() {
      URI uri = GrpcUtil.authorityToUri(defaultAuthority);
      if (uri.getHost() != null) {
        return uri.getHost();
      }
  
      return defaultAuthority;
    }
docs: Gets the overridden authority hostname.  If the authority is overridden to be an invalid
  authority, uri.getHost() will (rightly) return null, since the authority is no longer
  an actual service.  This method overrides the behavior for practical reasons.  For example,
  if an authority is in the form "invalid_authority" (note the "_"), rather than return null,
  we return the input.  This is because the return value, in conjunction with getOverridenPort,
  are used by the SSL library to reconstruct the actual authority.  It /already/ has a
  connection to the port, independent of this function.
  
  <p>Note: if the defaultAuthority has a port number in it and is also bad, this code will do
  the wrong thing.  An example wrong behavior would be "invalid_host:443".   Registry based
  authorities do not have ports, so this is even more wrong than before.  Sorry.