def payload_parser
      @payload_parser ||= if @receive_raw_payload
                            ->(payload) { payload }
                          else
                            ->(payload) {
                              ActiveSupport::HashWithIndifferentAccess.new(JSON.parse(payload))
                            }
                          end
    end
def payload_parser
      @payload_parser ||= if @receive_raw_payload
                            ->(payload) { payload }
                          else
                            ->(payload) {
                              ActiveSupport::HashWithIndifferentAccess.new(JSON.parse(payload))
                            }
                          end
    end
Returns a proc that, when called with the payload, parses it according to the configuration.

 By default, this will assume the payload is JSON, parse it, and return a HashWithIndifferentAccess.