removed fast-track for items whose post already exists

Since we want to be able to track the progress of the import, and we do it by checking the time of the oldest processed (not queued) item, we need to make sure that all items are put into the queue to be processed by PostDownloader in order

app/models/importable.rb

···
       errors.add(:queue, 'must be nil if already processed') if queue && post
     end
 
-    def import_item!
+    def import_item!(args = {})
       post_uri = AT_URI(self.post_uri)
       return nil if !post_uri.is_post?
 
-      if post = Post.find_by_at_uri(post_uri)
-        self.post = post
-        self.post_uri = nil
-        self.queue = nil
-      end
-
+      self.assign_attributes(args)
       self.save!
       self
     end

app/models/user.rb

···
       like = self.new_from_record(like_uri, record)
       return nil if like.nil? || self.where(rkey: like.rkey).exists?
 
-      like.assign_attributes(args)
-      like.import_item!
+      like.import_item!(args)
     end
   end
 
···
       repost = self.new_from_record(repost_uri, record)
       return nil if repost.nil? || self.where(rkey: repost.rkey).exists?
 
-      repost.assign_attributes(args)
-      repost.import_item!
+      repost.import_item!(args)
     end
   end
 
···
       quote = self.new_from_record(post_uri, record)
       return nil if quote.nil? || self.where(rkey: quote.rkey).exists?
 
-      quote.assign_attributes(args)
-      quote.import_item!
+      quote.import_item!(args)
     end
   end
 
···
       pin = self.new_from_record(post_uri, record)
       return nil if pin.nil? || self.where(rkey: pin.rkey).exists?
 
-      pin.assign_attributes(args)
-      pin.import_item!
+      pin.import_item!(args)
     end
   end