code: def build_soap!(&block)
        opts = { :server_version => server_version, :impersonation_type => impersonation_type, :impersonation_mail => impersonation_address }
        opts[:time_zone_context] = @time_zone_context if @time_zone_context
        EwsBuilder.new.build!(opts, &block)
      end
docs: Build the common elements in the SOAP message and yield to any custom elements.