Revert "Revert "Merge branch 'master' of https://github.com/discourse/discourse""

This reverts commit 20780a1eee.

* SECURITY: re-adds accidentally reverted commit:
  03d26cd6: ensure embed_url contains valid http(s) uri
* when the merge commit e62a85cf was reverted, git chose the 2660c2e2 parent to land on
  instead of the 03d26cd6 parent (which contains security fixes)

app/models/topic.rb

@@ -33,11 +33,11 @@ class Topic < ActiveRecord::Base
   end
 
   def self.thumbnail_sizes
-    [ self.share_thumbnail_size ]
+    [ self.share_thumbnail_size ] + DiscoursePluginRegistry.topic_thumbnail_sizes
   end
 
-  def thumbnail_job_redis_key(extra_sizes)
-    "generate_topic_thumbnail_enqueue_#{id}_#{extra_sizes.inspect}"
+  def thumbnail_job_redis_key(sizes)
+    "generate_topic_thumbnail_enqueue_#{id}_#{sizes.inspect}"
   end
 
   def filtered_topic_thumbnails(extra_sizes: [])
@@ -79,7 +79,7 @@ class Topic < ActiveRecord::Base
     if SiteSetting.create_thumbnails &&
        enqueue_if_missing &&
        records.length < thumbnail_sizes.length &&
-       Discourse.redis.set(thumbnail_job_redis_key(extra_sizes), 1, nx: true, ex: 1.minute)
+       Discourse.redis.set(thumbnail_job_redis_key(thumbnail_sizes), 1, nx: true, ex: 1.minute)
 
       Jobs.enqueue(:generate_topic_thumbnails, { topic_id: id, extra_sizes: extra_sizes })
     end
@@ -1476,6 +1476,13 @@ class Topic < ActiveRecord::Base
     private_topic
   end
 
+  def update_excerpt(excerpt)
+    update_column(:excerpt, excerpt)
+    if archetype == "banner"
+      ApplicationController.banner_json_cache.clear
+    end
+  end
+
   def pm_with_non_human_user?
     sql = <<~SQL
     SELECT 1 FROM topics