Add a find-or-create macro

[fractaledmind]

Imagine a scenario like this. We have a workflow where we need the author of a Slack message. Maybe a webhook has already processed and created our internal database representation, maybe it hasn't. So, in our job, we need to

1. try and find the internal record
2. if we don't have it, make an API call to fetch the data
3. if the API read succeeds, create the internal record
4. find the newly created internal record and set the variable

for example:

def find_author
  self.slack_author = event.installation.profiles.find_by(uid: @user_uid)
end

def fetch_unknown_author_from_slack
  return [] if @slack_author

  api_response = event.installation.client.user(uid: @user_uid)
  if api_response[:ok]
    [Slack::ProcessProfileSlackJob.with(event.installation, api_response[:user])]
  else
    raise DoNotRetryJob
  end
end

def ensure_author_known
   self.slack_author ||= event.installation.profiles.find_by(uid: @user_uid)
  raise DoNotRetryJob and return if @slack_author.nil?
end

Should this be something that the DSL makes more straight-forward?