Use message variable in slack_notifier for attachment text via options

[daino3]

I might be missing something in the code, or it might simply be a documentation thing, but I don't see an easy way to take the message variable in the slack_notifier#call and reuse it from within the options hash for setting up an attachment.

Something like:

# slack_notifier.rb

def call(exception, options={})
  message = "An exception occurred: '#{exception.message}'"
  message += " on '#{exception.backtrace.first}'" if exception.backtrace

  message = enrich_message_with_data(message, options)
  message = enrich_message_with_backtrace(message, exception) if exception.backtrace

  if  @message_opts[:attachments].any? && send_to_slack_as_attachment # config variable
    @message_opts[:attachments].each do | attachment |
      attachment[:text] = message
    end
  end
  @notifier.ping(message, @message_opts) if valid?
end

[nunosilva800]

Yeah, #299 didn't really fix this once and for all...

We can't add additional attachments because of @message_opts.merge(attachments: attchs)
https://github.com/smartinez87/exception_notification/blob/v4.1.2/lib/exception_notifier/slack_notifier.rb#L41

It would be nice to have at least this ability:

    additional_parameters: {
      attachments: [
        fields: [{ title: 'Project', value: "P-A" }]
      ]
    }