Move feeds association to HasAFeed concern and check if assoc. exists
user
```ruby
module HasAFeed
  extend ActiveSupport::Concern

  included do

    has_many :entities_imported_from_feed, as: :entity
    has_many :feeds, through: :entities_imported_from_feed

    def imported_from_feed_onestop_id=(value)
      feed = Feed.find_by!(onestop_id: value)
      self.feeds << feed unless self.feeds.exists?(feed)
    end

  end
end
```
assistant